Neurohypophyseal Diabetes Insipidus

MONDO:0007450 Pathograph 24 Show in embeddings browser central diabetes insipidus pituitary gland disorder

A hereditary deficiency of arginine vasopressin, transmitted in almost every family as an autosomal dominant trait, that presents in infancy or early childhood with hypotonic polyuria and compensatory polydipsia and worsens over years. The disease is not caused by loss of one working copy of AVP. A heterozygous mutation - almost always in the signal peptide or in the neurophysin II moiety of the prepro-vasopressin precursor - yields a folding-incompetent precursor that cannot leave the endoplasmic reticulum of the magnocellular neurons of the supraoptic and paraventricular nuclei. Part of it is cleared by ER-associated degradation; the rest forms disulfide-linked fibrillar aggregates that also trap the wild-type precursor made from the normal allele. The retained aggregate first disables hormone synthesis and secretion and then, over a longer timescale, kills the neuron by autophagy-associated death. That two-stage toxic gain of function is what explains the two features a haploinsufficiency model cannot: onset months to years after birth rather than at birth, and relentless progression despite one intact allele. Treatment is desmopressin, which replaces the missing hormone without touching the neuronal disease. A separate and much rarer autosomal recessive form exists, caused by homozygosity for AVP p.Pro26Leu, in which a weakly active hormone is synthesised, trafficked and secreted normally; there is no ER retention and no neuronal loss, and it is modelled here as a subtype precisely because its mechanism is the contrast case.

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Classifications

Harrison's Part

Mechanistic Nosology

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Inheritance

Autosomal dominant HP:0000006

The usual mode. Fully penetrant heterozygous AVP mutations transmit through successive generations, and each child of an affected parent is at 50 per cent risk. Penetrance being complete does not mean expression is uniform: age at onset and severity vary widely between and within families, so an apparently mildly affected relative is still a carrier.

Autosomal dominant inheritance

Show evidence (2 references)

PMID:31785344 SUPPORT Other

"The disease, manifesting in infancy or early childhood and gradually progressing in severity, is caused by fully penetrant heterozygous mutations in the gene encoding prepro-vasopressin-neurophysin II, the precursor of the antidiuretic hormone arginine vasopressin (AVP)."

States full penetrance and heterozygosity, which together define the dominant mode here.

PMID:31588537 SUPPORT Other

"Most commonly, the disease is transmitted in an autosomal dominant fashion; very rarely, autosomal recessive inheritance has been observed."

Gives the relative frequency of the two modes, which is why the dominant form is treated as the default in this entry.

Autosomal recessive HP:0000007

Rare, and reported in consanguineous families. Homozygosity for AVP p.Pro26Leu causes disease while heterozygous parents are entirely asymptomatic - the clean genetic demonstration that this allele does not have the dominant alleles' toxic property. Deletion of the AVP locus is the other recorded recessive route.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:10369876 SUPPORT Human Clinical

"We studied an unusual Palestinian family consisting of asymptomatic first cousin parents and three children affected with neurohypophyseal diabetes insipidus, suggesting autosomal recessive inheritance."

The pedigree evidence for recessive transmission, including the unaffected heterozygous parents.

PMID:27156762 SUPPORT Other

"In most affected families, the disease is transmitted in an autosomal dominant manner, whereas autosomal recessive forms are much less frequent."

Places the recessive mode as much less frequent, which is how it is weighted in this entry.

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Subtypes

Autosomal dominant familial neurohypophyseal diabetes insipidus

AVP hgnc:894 Autosomal dominant inheritance

The usual form, accounting for the great majority of families. A single heterozygous AVP allele encoding a folding-incompetent precursor is sufficient to cause disease, through retention and aggregation of the precursor in the endoplasmic reticulum of vasopressinergic neurons rather than through loss of hormone dosage. Onset is postnatal and the deficiency deepens with age.

Show evidence (1 reference)

PMID:31785344 SUPPORT Other

Establishes the dominant subtype as fully penetrant, heterozygous, of postnatal onset and progressive - the four features that separate it from the recessive subtype below.

Autosomal recessive familial neurohypophyseal diabetes insipidus (AVP p.Pro26Leu)

AVP hgnc:894 Autosomal recessive inheritance

A rare recessive form, reported in consanguineous Palestinian kindreds homozygous for AVP c.301C>T, replacing Pro26 of the precursor - Pro7 of the mature nonapeptide - with leucine. Heterozygous parents are unaffected. The mechanism is entirely different from the dominant form: the prohormone traffics through the secretory pathway normally and reaches the circulation, but the hormone it delivers binds the V2 receptor roughly thirtyfold less well, so circulating immunoreactive vasopressin is high while antidiuretic activity is low. This is a hormone-activity defect, not an ER storage disease, and there is no reason to expect vasopressinergic neurodegeneration in it.

Show evidence (3 references)

PMID:10369876 SUPPORT Human Clinical

"All three affected children were homozygous and the parents heterozygous for a single novel mutation (C301->T) in exon 1, replacing Pro7 of mature AVP with Leu (Leu-AVP)."

Establishes the recessive segregation and the causal allele, numbered here by residue of the mature hormone rather than of the precursor.

PMID:10369876 SUPPORT In Vitro

"Leu-AVP was a weak agonist with approximately 30-fold reduced binding to the human V2 receptor."

Quantifies the receptor-binding defect that makes this a hormone-activity subtype rather than a hormone-deficiency subtype.

PMID:27156762 SUPPORT Other

"Recessive transmission results from AVP with reduced biologic activity or the deletion of the locus."

Confirms that recessive inheritance in this disease has a distinct mechanistic basis, and records the second recessive route - locus deletion - which is not covered by the p.Pro26Leu allele.

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Pathophysiology

Mutant Prepro-Vasopressin Misfolding

Mechanism confidence: Established

The initiating lesion. A heterozygous point mutation in AVP - typically in the signal peptide or at a residue of the neurophysin II moiety that the precursor needs in order to fold and dimerise - yields a prepro-vasopressin that is folding incompetent. Signal-peptide alleles such as Ala(-1)Thr additionally prevent cleavage of the signal sequence, so an uncleaved 23-kDa precursor accumulates. The lesion is in the precursor's ability to fold, not in the hormone it eventually encodes, which is why the mature nonapeptide is normal in these families and why a hormone-replacement drug works while the neuronal disease continues.

AVP hgnc:894

Genetic context AVP hgnc:894 variant_origin: GERMLINE zygosity: HETEROZYGOUS functional_impact_category: DOMINANT_NEGATIVE

The consequence of the variant is not loss of the encoded hormone's activity. The mutant precursor acquires a toxic aggregation property and, because it still dimerises with the product of the normal allele, drags wild-type precursor into the same ER-retained aggregate. That is a dominant-negative consequence layered on a toxic gain, and it is why the single normal allele does not rescue the phenotype. Contrast the recessive p.Pro26Leu allele, where the consequence really is reduced activity of the secreted hormone and heterozygotes are well.

protein folding in endoplasmic reticulum GO:0034975 ⚠ ABNORMAL

Downstream

Endoplasmic Reticulum Retention and Fibrillar Aggregation A precursor that cannot fold cannot pass ER quality control, so it is retained rather than packaged into dense-core secretory granules.

Show evidence (6 references)

PMID:31785344 SUPPORT Other

"Studies in cells expressing pathogenic mutants and knock-in rodent models have shown that the mutant precursors are folding incompetent and fail to exit the endoplasmic reticulum (ER), as occurs normally with proteins that have entered the regulated secretory pathway."

States the folding-incompetence of the mutant precursor, which is the lesion this node models.

PMID:10369876 SUPPORT Human Clinical

"All published mutations affect the signal peptide or the neurophysin-II carrier protein and are presumed to interfere with processing of the preprohormone, leading to neuronal damage."

Gives the position of the dominant alleles within the precursor, which is the structural regularity this node depends on.

PMID:10085151 SUPPORT In Vitro

"An in vivo cross-linking reaction revealed homo- and heterodimer formation between WT and mutant precursors. Mutant precursors were also shown to impair intracellular trafficking of WT precursors from the endoplasmic reticulum to the Golgi apparatus."

The experimental basis for `functional_impact_category: DOMINANT_NEGATIVE` on this node: the mutant precursor both dimerises with the wild-type product and blocks its ER-to-Golgi transit, which is why one normal allele does not rescue. The entry's `notes:` cited this paper for exactly that claim, so it now carries the evidence item rather than only a mention.

+ 3 more references

Endoplasmic Reticulum Retention and Fibrillar Aggregation

Mechanism confidence: Established

The retained precursor accumulates in the ER lumen of vasopressinergic magnocellular neurons. Some is retrotranslocated and destroyed by ER-associated degradation, but ERAD capacity is finite; the remainder self-associates into large disulfide-linked fibrillar aggregates. Crucially the aggregates are not pure mutant: wild-type precursor made from the normal allele is trapped in them, so one bad allele removes more than half the hormone-making capacity. In the knock-in mouse the aggregates are initially walled off in a sub-compartment of the ER and only later scatter through a dilated ER lumen, which is the ultrastructural correlate of the disease becoming progressive.

vasopressin-secreting magnocellular cell CL:4023109

ERAD pathway GO:0036503 ↑ INCREASED

endoplasmic reticulum GO:0005783

supraoptic nucleus UBERON:0001929 paraventricular nucleus of hypothalamus UBERON:0001930

Animal models

FNDI knock-in mouse (mutant neurophysin II) Mouse recapitulates Aggregates form in the endoplasmic reticulum of supraoptic AVP neurons and grow in step with urine volume, so the model reproduces the retained aggregate in the correct cell type and in the correct temporal relation to the phenotype.

FNDI knock-in mouse (mutant neurophysin II) Mouse rescues The chemical chaperone 4-phenylbutyrate reduced mutant protein accumulation in the ER of these mice, increased AVP release, cut urine volume and attenuated neuron loss under salt loading. This is the pharmacological test of the mechanism: relieving the ER burden improves both the hormone deficit and the degeneration, which is what a proteotoxicity model predicts and a haploinsufficiency model does not.

Sel1L-Hrd1 ERAD-deficient mouse Mouse recapitulates Reproduces the ER retention and intermolecular disulfide-bonded aggregation of proAVP that the human dominant alleles produce, and identifies protein disulfide isomerase activity as what drives the inappropriate cross-linking.

Downstream

Vasopressin Neuron Secretory Dysfunction Aggregate accumulation disables hormone production and release before any cell is lost, which is the step that makes polyuria precede neurodegeneration.

Endoplasmic Reticulum Stress and Autophagy Induction Once aggregates exceed the ER-associated compartment that contains them and spill into a dilating ER lumen, the cell turns to autophagy.

Show evidence (5 references)

PMID:31588537 SUPPORT Other

"Current data show that retained mutants fail to be eliminated by the cell's quality control system and accumulate in fibrillar aggregations within the ER."

States both halves of this node - quality-control failure and fibrillar aggregation in the ER.

PMID:31785344 SUPPORT Other

"A portion of these mutants is eliminated via ER-associated degradation (ERAD) by proteasomes after retrotranslocation to the cytosol. Another portion forms large disulfide-linked fibrillar aggregates within the ER, in which wild-type precursor is trapped."

Gives the two fates of the retained precursor and, decisively for the dominance of the disease, records that wild-type precursor is trapped in the aggregate.

PMID:29961215 SUPPORT Model Organism

"Electron microscopic analyses revealed that aggregates were confined to a sub-compartment of the endoplasmic reticulum (ER), ER-associated compartment (ERAC), in AVP neurons of FNDI mice under normal conditions."

Establishes the in-vivo ultrastructure of the aggregate in the neuron the disease actually affects, and its initial containment.

+ 2 more references

Endoplasmic Reticulum Stress and Autophagy Induction

Mechanism confidence: Established

The aggregate burden imposes sustained stress on the ER of the vasopressin neuron and drives autophagy. Phagophores form around the aggregate-laden ER and engulf it. This is initially a protective response: it is the cell's attempt to clear what ERAD could not. It becomes destructive because it does not stop - continuous autophagy strips the neuron of organelles, including the ER itself.

vasopressin-secreting magnocellular cell CL:4023109

response to endoplasmic reticulum stress GO:0034976 ↑ INCREASED macroautophagy GO:0016236 ↑ INCREASED

Animal models

Cys67stop FNDI transgenic rat Rat recapitulates Lysosomal and late-endosomal markers are upregulated specifically in the cells expressing the mutant transgene, and the aggregate-containing vesicles are immunoreactive for cathepsin D, endolyn and LAMP1.

Downstream

Magnocellular Vasopressin Neuron Loss Unrelenting autophagy consumes the neuron's organelles and ends in cell death rather than in clearance.

Vasopressin Neuron Secretory Dysfunction A second, transcript-level route from the same stress. ER stress shortens the poly(A) tail of AVP mRNA and lowers its expression, which throttles the supply of new precursor. The cell is reducing the unfolded-protein load it has to handle, and the price is hormone output.

Show evidence (2 references)

PMID:41045372 SUPPORT Model Organism

"Three-dimensional analysis revealed that phagophores enveloped aggregates located within the dilated ER. Serial imaging further demonstrated a physical connection between these phagophores and intact ER membranes."

Three-dimensional electron microscopy of the affected neuron showing the autophagic machinery engaging the aggregate-containing ER directly, and forming from ER membrane rather than arriving from elsewhere.

PMID:12153465 SUPPORT Model Organism

"Swollen vesicles containing Cys67stop are immunoreactive for cathepsin D (a lysosomal protease), endolyn (a marker of late endosomes) and lysosomal associated membrane protein 1, suggesting that they may be degradative autolysosomes."

Identifies the vesicles that accumulate around the mutant protein as degradative autolysosomes, which is the autophagic arm of this node.

Vasopressin Neuron Secretory Dysfunction

Mechanism confidence: Established

Before any neuron dies, the surviving neurons stop working. AVP mRNA in the supraoptic nucleus falls, mature hormone output collapses, and the regulated secretory pathway is starved of cargo because the precursor never reaches the trans-Golgi network. This node is the reason the disease is progressive from an early age and yet compatible with a normal neuron count for a long time, and it is separated from the neuron-loss node deliberately: the mouse data show polyuria advancing substantially while the AVP-expressing cell count is still intact.

vasopressin-secreting magnocellular cell CL:4023109

vasopressin secretion GO:0030103 ↓ DECREASED

Animal models

FNDI knock-in mouse (mutant neurophysin II) Mouse recapitulates AVP mRNA in the supraoptic nucleus falls while the AVP-expressing cell count is unchanged, which is the direct in-vivo demonstration that secretory failure precedes cell loss.

Downstream

Progressive Arginine Vasopressin Deficiency Neurons that cannot transcribe, process or release the hormone deliver less of it to the circulation, and do so increasingly over time.

Show evidence (2 references)

PMID:19297548 SUPPORT Model Organism

"Analyses with in situ hybridization revealed that expression of AVP mRNA was significantly decreased in the SON in the heterozygous mice compared with that in wild-type mice. Counting cells expressing AVP mRNA in the SON indicated that polyuria had progressed substantially in the absence of..."

The direct evidence for this node as a distinct step - transcript and function fall while the cells are still there and still counted.

PMID:10443701 SUPPORT Human Clinical

"The clinical studies showed a severe progressive deficiency of plasma and urinary AVP that manifested during childhood."

The human counterpart of the same claim, measured as hormone output in an affected kindred rather than as transcript in a mouse.

Magnocellular Vasopressin Neuron Loss

Mechanism confidence: Established

The end state of the proteotoxic cascade. Vasopressinergic magnocellular neurons of the supraoptic and paraventricular nuclei degenerate, which is what post-mortem examination of affected adults shows and what makes this disease, in Rutishauser's phrase, a neurodegeneration confined to one neuronal population. Loss is not all-or-nothing and is accelerated by osmotic demand: in the knock-in mouse, sustained water deprivation - which forces the mutant neurons to work - destroys 30 to 40 per cent of them within twelve weeks. Oxytocin magnocellular neurons in the same nuclei are spared, because they do not make the mutant cargo.

vasopressin-secreting magnocellular cell CL:4023109

neuron apoptotic process GO:0051402 ↑ INCREASED

supraoptic nucleus UBERON:0001929 paraventricular nucleus of hypothalamus UBERON:0001930

Animal models

FNDI knock-in mouse (mutant neurophysin II) Mouse partially recapitulates Neuronal loss does occur, but only when the mutant neurons are driven by sustained osmotic demand; 30 to 40 per cent of AVP neurons are lost after twelve weeks of water deprivation.

Brattleboro rat Rat fails to recapitulate The Brattleboro rat retains its magnocellular vasopressin neurons. It has the hormone deficiency without the neurodegeneration, so it cannot be used to study the proteotoxic arm of the human disease and cannot be used to argue that the arm is unnecessary.

Downstream

Progressive Arginine Vasopressin Deficiency Neurons that have died cannot be recruited, so this arm makes the deficiency irreversible where the secretory-dysfunction arm alone might not be.

Show evidence (3 references)

PMID:31785344 SUPPORT Human Clinical

"Post mortem studies in affected adults have shown cell degeneration in vasopressinergic hypothalamic nuclei."

The human neuropathological observation on which the whole neurotoxicity model was originally built.

PMID:31588537 SUPPORT Other

"Autosomal dominant neurohypophyseal DI may thus be viewed as a neurodegenerative disease confined to vasopressinergic neurons."

States the framing this node adopts, including the cell-type restriction that distinguishes it from a general proteinopathy.

PMID:29961215 SUPPORT Model Organism

"Furthermore, the cytoplasm was entirely occupied with large vacuoles in AVP neurons of FNDI mice subjected to water deprivation for 12 weeks, at which stage 30-40% of AVP neurons were lost."

Quantifies the loss in vivo and ties its rate to osmotic demand on the mutant neurons.

Secreted Weakly Active Vasopressin

Mechanism confidence: Established

The recessive contrast mechanism, present only in the AR P26L subtype. The p.Pro26Leu precursor is not folding incompetent: it moves through the secretory pathway, is packaged into granules in the cell processes and is released, so there is no ER retention, no aggregate and no proteotoxic threat to the neuron. What reaches the circulation is a poor V2 receptor agonist. Immunoreactive vasopressin in serum is therefore high, not low - the opposite of the dominant disease - while antidiuresis fails all the same. This node is included because the recessive form is otherwise easy to read as a milder version of the same disease, and it is not.

AVP hgnc:894

Downstream

Impaired Renal Free Water Reabsorption A weak V2 agonist circulating at high concentration still fails to generate an adequate antidiuretic signal at the collecting duct.

Show evidence (3 references)

PMID:15356057 SUPPORT In Vitro

"Confocal laser scanning microscopy showed accumulation of the Y21H prohormone in the endoplasmic reticulum, whereas the P26L prohormone and/or processed products were localized in secretory granules in the cellular processes."

Side-by-side demonstration in one experiment that the dominant allele is ER-retained and the recessive one is not, which is the whole basis for modelling them as different mechanisms.

PMID:15356057 SUPPORT In Vitro

"Thus, the recessive mutation does not seem to affect the intracellular trafficking but rather the final processing of the prohormone."

The authors' summary of where the recessive defect lies, which is downstream of everything the dominant mechanism turns on.

PMID:10369876 SUPPORT Human Clinical

"Measured by radioimmunoassay with a synthetic Leu-AVP standard, serum Leu-AVP levels were elevated in all three children and further increased during water deprivation to as high as 30 times normal."

Establishes in patients that the mutant hormone is made, secreted and osmotically regulated - so the deficiency in this subtype is of hormone action, not of hormone supply.

Progressive Arginine Vasopressin Deficiency

Mechanism confidence: Established

The systemic consequence: circulating arginine vasopressin falls below what is needed to concentrate urine, and continues to fall over years as more neurons become dysfunctional and then die. Partial deficiency is common early, so the water deprivation test can be equivocal in a child who will later have unmistakable disease. Osmoregulated thirst is intact, which is what keeps most patients in water balance and turns the deficiency into a drinking problem rather than a hypernatraemia problem.

Downstream

Impaired Renal Free Water Reabsorption The endocrine-to-renal step. Circulating vasopressin is the ligand for the V2 receptor on the collecting duct principal cell, and without it the aquaporin-2 trafficking that makes the duct water-permeable does not happen.

Show evidence (2 references)

PMID:31588537 SUPPORT Other

"Dominant mutations cause retention of the hormone precursor in the endoplasmic reticulum (ER) of vasopressinergic neurons in the hypothalamus, resulting in cellular dysfunction and eventually neuronal death."

Traces the chain from ER retention through dysfunction to death, the two upstream arms that converge on this node.

PMID:29961215 SUPPORT Other

"Familial neurohypophysial diabetes insipidus (FNDI), characterized by delayed-onset progressive polyuria and loss of arginine vasopressin (AVP) neuron, is an autosomal dominant disorder caused by AVP gene mutations."

States the delayed onset and progressive character that this node is responsible for, as opposed to a congenital fixed deficit.

Impaired Renal Free Water Reabsorption

Mechanism confidence: Established

Without an adequate vasopressin signal at the V2 receptor of the collecting duct principal cell, aquaporin-2 is not inserted into the apical membrane, the duct stays water-impermeable and the osmotic gradient of the medulla cannot be used. Large volumes of maximally dilute urine are lost. Everything clinical in this disease follows from here.

renal water absorption GO:0070295 ↓ DECREASED

collecting duct of renal tubule UBERON:0001232

Downstream

Polyuria Water that is not reabsorbed in the collecting duct is excreted, so the urine volume is large and its osmolality low.

Hyposthenuria The same failure of collecting-duct water permeability that raises the volume lowers the concentration, so the two renal phenotypes are one event measured two ways.

Nocturia Antidiuresis fails around the clock, so the obligate water loss continues overnight when drinking has stopped.

Polydipsia Urinary water loss raises plasma osmolality, and intact osmoreceptor-driven thirst then produces the compensatory drinking.

Hypernatremic Dehydration Only when thirst cannot be acted on - in an infant, or in anyone without free access to water - does the water loss become a sodium and volume emergency.

Show evidence (1 reference)

PMID:27156762 SUPPORT Other

"Neurohypophyseal diabetes insipidus is characterized by polyuria and polydipsia owing to partial or complete deficiency of the antidiuretic hormone, arginine vasopressin (AVP)."

States that the renal water-handling failure and its clinical expression follow from vasopressin deficiency, which is the step this node carries.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

Digestive 1

Vomiting OCCASIONAL HP:0002013

Show evidence (1 reference)

PMID:19897608 SUPPORT Human Clinical

"Three Palestinian cousins presented with failure to thrive, vomiting, irritability, and fever."

Names vomiting as one of the presenting features in affected infants.

Genitourinary 3

Polyuria OBLIGATE HP:0000103

Course: PROGRESSIVE

Show evidence (2 references)

PMID:38087160 SUPPORT Human Clinical

"The polyuria-polydipsia syndrome is characterized by a high urinary output of more than 50 ml per kg body weight per 24 h, accompanied by polydipsia of more than 3 L a day"

Gives the quantitative threshold used clinically to call the urine output polyuric, and pairs it with the polydipsia phenotype below.

PMID:19897608 SUPPORT Human Clinical

"Patients typically present between 1 and 6 years of age with polyuria and polydipsia."

Establishes polyuria as the typical presenting phenotype and gives the age window, which is the postnatal-onset claim this entry rests on.

Hyposthenuria VERY_FREQUENT HP:0003158

Show evidence (1 reference)

PMID:19897608 SUPPORT Human Clinical

"Patients developed hypernatremia (154-163 mmol/l) and serum hyperosmolality (>320 mOsm/kg), while urine osmolality remained between 73 and 229 mOsm/kg."

The defining dissociation, with numbers: serum hyperosmolality above 320 mOsm/kg alongside urine osmolality as low as 73 mOsm/kg.

Nocturia FREQUENT HP:0000017

Temporal: NOCTURNAL

Show evidence (1 reference)

PMID:38087160 SUPPORT INDIRECT Human Clinical

"The initial treatment aim is to reduce nocturia, and therefore, the first desmopressin dose is usually given at bedtime, and if needed, a daytime dose is added."

Establishes nocturia as a recognised and clinically targeted manifestation. The quote supports it through the treatment aim rather than by naming a frequency, hence directness INDIRECT.

Metabolism 1

Hypernatremic Dehydration OCCASIONAL HP:0004906

Show evidence (1 reference)

PMID:19897608 SUPPORT Human Clinical

"Patients developed hypernatremia (154-163 mmol/l) and serum hyperosmolality (>320 mOsm/kg)"

Documents the hypernatraemic presentation with measured sodium and osmolality in infants who could not drink to compensate.

Nervous System 1

Polydipsia OBLIGATE HP:0001959

Show evidence (2 references)

PMID:38087160 SUPPORT Human Clinical

"In most patients, osmoregulated thirst perception is intact and adequate fluid intake compensates for urinary water loss"

Establishes that the polydipsia is intact-thirst compensation rather than a primary drinking disorder, which is the distinction the differential turns on.

PMID:33433888 SUPPORT Human Clinical

"Patients showed progressive symptoms of polyuria and polydipsia, but with wide variability in severity and age at onset."

Documents the paired phenotype across five kindreds and records the variability in onset and severity that complicates family screening.

Growth 1

Failure to Thrive in Infancy OCCASIONAL HP:0001531

Show evidence (1 reference)

PMID:19897608 SUPPORT Human Clinical

"Three Palestinian cousins presented with failure to thrive, vomiting, irritability, and fever."

Records the infantile presentation directly, including the non-specific symptoms that accompany it.

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Genetic Associations

AVP (Heterozygous mutation of the signal peptide or neurophysin II moiety, autosomal dominant; homozygous p.Pro26Leu, autosomal recessive)

Gene: AVP hgnc:894 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (3 references)

PMID:33433888 SUPPORT Human Clinical

"These consisted of one initiation codon mutation in the signal peptide coding region (c.2T > C, p.Met1?), three missense mutations in the neurophysin II (NPII) coding region (c.154T > C, p.Cys52Arg; c.289C > G, p.Arg97Gly; and c.293G > C, p.Cys98Ser), and one nonsense mutation in the NPII coding..."

Illustrates the allelic spectrum and its confinement to the signal peptide and neurophysin II across one cohort of five families.

PMID:33433888 SUPPORT Human Clinical

"Patients showed progressive symptoms of polyuria and polydipsia, but with wide variability in severity and age at onset. No clear genotype-phenotype correlation was observed."

The basis for the statement that genotype does not stratify the phenotype.

PMID:31588537 SUPPORT Other

"Hereditary neurohypophyseal DI is caused by mutations in the gene encoding the antidiuretic hormone vasopressin (AVP) and its carrier protein neurophysin II (NPII)."

Establishes AVP as the causative gene for the hereditary disease, covering both the hormone and the carrier-protein moieties of the same transcript.

💊

Medical Actions

Desmopressin

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: desmopressin CHEBI:4450

Platform: Peptide

The standard of care and, in practice, the whole of treatment. Desmopressin is a synthetic vasopressin analogue differing by two amino acids, which lengthen its half-life and remove the vasopressor activity, leaving a selective V2 agonist. Oral, intranasal and parenteral formulations exist; oral is now preferred on tolerability and safety grounds. It replaces the missing hormone and does nothing whatever to the aggregating precursor upstream, so the neuronal disease continues underneath a controlled phenotype - which is why disease-modifying approaches are of interest even though symptom control is good. Dosing is individualised and starts at bedtime to control nocturia.

Mechanism Target:

BYPASSES Impaired Renal Free Water Reabsorption — Supplying an exogenous V2 agonist restores aquaporin-mediated water reabsorption at the collecting duct without restoring endogenous hormone production, so it bypasses every upstream node rather than correcting any of them.

Show evidence (1 reference)

PMID:38087160 SUPPORT Human Clinical

"Desmopressin differs from AVP by two amino acids and is available in parenteral, oral and nasal formulations, providing effective long-term control of polyuria."

Identifies the agent as a hormone analogue acting at the renal receptor and records that it controls the renal phenotype long term.

Show evidence (3 references)

PMID:38087160 SUPPORT Human Clinical

"Desmopressin, a synthetic AVP analogue and selective V2 receptor agonist, is the current standard of care and is usually initiated after the diagnosis of AVP-D is confirmed"

Establishes desmopressin as the standard of care and names its pharmacological class.

PMID:38087160 SUPPORT Human Clinical

"Desmopressin treatment provides immediate symptomatic relief; however, the main complication is dilutional hyponatremia and its associated risk of cerebral edema, seizure, coma and even death"

The principal hazard of the treatment. It is recorded on the treatment itself rather than as a phenotype because it is iatrogenic, not a feature of the disease.

PMID:19897608 SUPPORT Human Clinical

"All patients responded to desmopressin."

Confirms responsiveness in the recessive subtype specifically, which is not obvious a priori: the endogenous hormone there is present but weak, so the drug works by supplying a full agonist rather than by filling a void.

Assured Access to Water and Fluid Management

Category: Therapeutic Action: supportive care Ontology label: Supportive Care NCIT:C15747

Platform: Behavioral / lifestyle

Not an afterthought. Because osmoregulated thirst is intact in almost all patients, free access to water is what actually maintains water balance, and the situations that remove it - fasting for surgery, vomiting or diarrhoeal illness, unconsciousness, an inpatient team unfamiliar with the condition - are the ones that kill. The management of dehydration when it occurs is replacement of roughly half the calculated free water deficit over the first 24 hours with hypotonic fluid.

Mechanism Target:

INHIBITS Hypernatremic Dehydration — Maintaining intake against an obligate renal water loss prevents the hypertonic decompensation, which is the only life-threatening event in the natural history of a treated patient.

Show evidence (1 reference)

PMID:38087160 SUPPORT Human Clinical

"Therefore, hypernatremia, an indicator of inadequate fluid balance, rarely occurs in AVP-D patients with free access to fluids"

States the protective effect directly - free access to fluids is what keeps hypernatraemia rare.

Show evidence (1 reference)

PMID:38087160 SUPPORT Human Clinical

"The main treatment goals in patients with AVP-D are the correction of pre-existing water deficits and the reduction of excessive urinary water loss."

States the two treatment goals, of which this intervention addresses the first and desmopressin the second.

🔬

Biochemical Markers

Plasma arginine vasopressin (Decreased)

Context: The direct measure of the deficiency in the dominant form. It falls progressively over childhood in parallel with urinary AVP. Note the sign reverses in the recessive P26L subtype, where immunoreactive hormone is high because a poorly active peptide is still being secreted - so a normal or elevated result does not exclude hereditary disease until the subtype is known. In practice AVP itself is rarely measured now; copeptin has replaced it because AVP is unstable and largely platelet-bound.

Pathograph Readouts

Readout Of Progressive Arginine Vasopressin Deficiency Positive Diagnostic

Directly reports the circulating hormone concentration that this node is about.

Show evidence (1 reference)

PMID:10443701 SUPPORT Human Clinical

"The clinical studies showed a severe progressive deficiency of plasma and urinary AVP that manifested during childhood."

Reports the analyte, its direction and its progressive course in an affected kindred.

Show evidence (1 reference)

PMID:19897608 SUPPORT Human Clinical

"Plasma AVP levels were low, and the posterior pituitary bright spot was absent on magnetic resonance imaging (MRI)."

Documents low plasma AVP measured in affected patients, together with the imaging correlate.

Plasma copeptin (Decreased)

Context: Copeptin is the C-terminal glycopeptide of the same prepro-vasopressin precursor, released in equimolar amounts with the hormone but far more stable, and it has displaced AVP as the assay of record. A stimulated copeptin that stays low is the diagnostic finding; a high unstimulated copeptin instead points to vasopressin resistance. Copeptin is also one of the two domains of the precursor that confers aggregation capacity, so in this disease the marker and the toxic species are parts of one molecule.

Pathograph Readouts

Readout Of Progressive Arginine Vasopressin Deficiency Positive Diagnostic

A surrogate for vasopressin secretion, measured after osmotic stimulation so that a low value means failure to secrete rather than absence of a stimulus.

Show evidence (1 reference)

PMID:30067922 SUPPORT Human Clinical

"In the latter test, plasma copeptin was measured when the plasma sodium level had increased to at least 150 mmol per liter after infusion of hypertonic saline."

Specifies how the readout is obtained - the osmotic stimulus that makes a low copeptin interpretable.

Show evidence (2 references)

PMID:38087160 SUPPORT Human Clinical

"Using the pre-defined copeptin cut-off of ≤ 4.9 mmol/L, patients with AVP-D were reliably distinguished from patients with primary polydipsia with a diagnostic accuracy of 97%."

Gives the operating threshold and its accuracy. Two things about this quote only make sense against the diagnosis section. The review prints the unit as mmol/L where the primary trial reports pmol per litre; the snippet quotes the cached source exactly and the correct unit is picked up from PMID:30067922 there. And its 97% is the review's rounding of the same measurement that section reports as 96.5% - same trial, same test, same 4.9 cutoff - not a second analysis. The cached record of PMID:30067922 is abstract-only; it gives 96.5% as the test's overall accuracy, and 95.2% for the partial-central-DI-versus-primary-polydipsia subgroup, and no 97%. So the reading rests on 96.5% being the only figure in that record which 97% could be a rounding of, not on a search of the full paper.

PMID:31785344 SUPPORT Other

"Aggregation capacity is independently conferred by two domains of the prohormone, namely the AVP moiety and the C-terminal glycopeptide (copeptin)."

Records that copeptin is one of the aggregation-competent domains, which is why this marker is mechanistically as well as diagnostically interesting here.

Urine osmolality (Decreased)

Context: Inappropriately low urine osmolality in the face of a rising plasma osmolality is the physiological signature of the disease. Values below 300 mOsm/kg after water deprivation, rising by more than 50 per cent on desmopressin, define complete arginine vasopressin deficiency; partial deficiency lands in an intermediate band that the water deprivation test handles poorly.

Pathograph Readouts

Readout Of Impaired Renal Free Water Reabsorption Positive Diagnostic

Reports the collecting duct's failure to concentrate, which is the renal node itself rather than the hormone deficit upstream of it.

Show evidence (1 reference)

PMID:38087160 SUPPORT Human Clinical

"Patients were urinary osmolality stays below 300 mosm/kg but increases over 50% upon desmopressin administration are diagnosed as having complete AVP-D."

Gives the diagnostic thresholds for this readout. The sentence is garbled in the source ("Patients were urinary osmolality stays") and is quoted verbatim as required.

Show evidence (1 reference)

PMID:19897608 SUPPORT Human Clinical

"while urine osmolality remained between 73 and 229 mOsm/kg"

Measured values in affected patients, showing how far below plasma the urine osmolality sits.

Serum sodium (Increased)

Context: Normal in a compensated patient with free access to water, so a normal sodium never excludes the diagnosis. It rises when compensation fails, and it is also the parameter that has to be watched in the opposite direction once desmopressin is started, because dilutional hyponatraemia is the main treatment complication.

Pathograph Readouts

Readout Of Hypernatremic Dehydration Positive Monitoring

Reports the decompensated state, and is monitored bidirectionally once desmopressin is in use.

Show evidence (1 reference)

PMID:19897608 SUPPORT Human Clinical

"Patients developed hypernatremia (154-163 mmol/l) and serum hyperosmolality (>320 mOsm/kg)"

Gives the measured sodium range in decompensated affected patients.

Show evidence (1 reference)

PMID:38087160 SUPPORT Human Clinical

"The first days of treatment should be followed by monitoring of plasma sodium to avoid hyponatremia. Once a stable dose of desmopressin is established, annual monitoring of plasma sodium and kidney function should be performed."

Establishes plasma sodium as the monitored analyte on treatment, which is the other half of why it is recorded here.

🔬

Diagnosis

Hypertonic saline-stimulated copeptin (PRESENT)

The current reference test. Plasma sodium is raised to at least 150 mmol/L with hypertonic saline and copeptin is measured at that point; a value at or below 4.9 pmol/L identifies vasopressin deficiency. It replaced the indirect water deprivation test on a head-to-head comparison in which it was substantially more accurate. It demands rapid bedside sodium measurement and close supervision, which is its practical cost.

Show evidence (1 reference)

PMID:30067922 SUPPORT Human Clinical

"Overall, among the 141 patients included in the analysis, the indirect water-deprivation test determined the correct diagnosis in 108 patients (diagnostic accuracy, 76.6%; 95% confidence interval [CI], 68.9 to 83.2), and the hypertonic saline infusion test (with a copeptin cutoff level of >4.9..."

The head-to-head accuracy comparison and the copeptin threshold, in the trial that established both.

Arginine-stimulated copeptin (PRESENT)

An alternative stimulation test proposed on grounds of simplicity: arginine is infused instead of hypertonic saline, so no bedside sodium monitoring and no induced hypernatraemia are needed. That practical advantage is the reason it was put forward, and it is what makes it usable where the reference test is not. The operating point is copeptin measured 60 minutes after the start of a body-weight-adapted infusion, with a cutoff of 3.8 pmol/L giving 93% diagnostic accuracy against primary polydipsia. Its main cost is nausea, which is not merely unpleasant: nausea and vomiting are themselves strong non-osmotic stimuli of AVP and copeptin release, so a symptomatic patient confounds the analyte the test measures, and a result obtained during severe nausea is interpretable only if copeptin stayed low. It is recorded here as an alternative rather than a replacement: sixty patients took part in both stimulation studies, and a post-hoc comparison within that overlap gave 100% diagnostic accuracy for hypertonic saline against 93% for arginine, which the review attributes to hypertonic saline being the stronger copeptin stimulus. What arginine buys in exchange is a simpler protocol and better tolerance.

The diagnostic-accuracy figures across this section come from different analyses, and only some of them can be lined up. Two are genuine within-cohort comparisons: the 141-patient trial supplies 96.5% for hypertonic saline against 76.6% for the water deprivation test, and the post-hoc analysis of the sixty patients who took part in both stimulation studies supplies 100% for hypertonic saline against 93% for arginine. What cannot be chained is one of those comparisons to the other: 100% and 96.5% are the same test measured in different patient sets, the sixty being those who also took part in the arginine study rather than an independent cohort. The 70-77% quoted on the water deprivation entry is a range across two prospective studies, one of them this same 141-patient trial, so the 76.6% sits inside that range rather than beside it.

Show evidence (8 references)

PMID:38087160 SUPPORT Other

"Due to its simplicity, arginine stimulated copeptin was put forward as alternative test procedure."

States both the test and the reason it exists, in the review that surveys the copeptin-based options. Graded OTHER because "was put forward as" is the review's own editorial framing rather than a reported result.

PMID:38087160 SUPPORT Human Clinical

"It was shown that copeptin measured 60 min after the start of the infusion using the cut-off level 3.8 pmol/L had the highest diagnostic accuracy of 93% to differentiate between patients with AVP-D and primary polydipsia [5]."

Gives the test's operating point - timing, cutoff and accuracy - without which the entry describes a test a reader cannot apply. Graded HUMAN_CLINICAL rather than OTHER because the sentence reports the result of the prospective study in patients with polyuria-polydipsia syndrome, which is what evidence_source classifies; the OTHER items added alongside it quote the review's own framing, recommendation or synthesis instead. That distinction governs the items added here; it is not a claim about how every one of this reference's items in this file is graded, several of which are review narrative carrying HUMAN_CLINICAL from earlier curation.

PMID:38087160 SUPPORT Human Clinical

"The most common adverse effect was mild nausea which occurred in 48% of the patients."

Quantifies the test's principal adverse effect in the same study cohort. Nearly half is high enough that it belongs in the description rather than only in a tolerability footnote.

+ 5 more references

Indirect water deprivation test (PRESENT)

The historical gold standard, still widely performed. Urine concentrating ability is assessed over a fluid-restriction period and then challenged with desmopressin. Its weakness is precisely where this disease often sits early on - partial deficiency - and its published cutoffs were derived from a single small study that was never prospectively validated.

Show evidence (1 reference)

PMID:38087160 SUPPORT Human Clinical

"In view of these limitations, it was not surprising that two prospective studies evaluating the diagnostic accuracy of the indirect water deprivation test found the diagnostic accuracy to be only 70–77%, with especially low accuracy in the difficult differentiation between partial AVP-D and PP patients"

Quantifies the test's accuracy and locates its failure in the partial-deficiency differential that matters most in this disease.

Absent posterior pituitary bright spot on T1 MRI (PRESENT)

The T1 hyperintensity of the normal posterior pituitary is attributed to vasopressin stored in neurosecretory granules, so its loss is the imaging correlate of the depleted and degenerating neurohypophyseal system and is the classic supporting observation in this disease. It is supporting rather than decisive: the bright spot is absent in only about 70 per cent of patients with vasopressin deficiency and in 39 per cent of patients with primary polydipsia, it disappears with age in healthy people, and it persists in some genuinely affected patients.

Show evidence (2 references)

PMID:19897608 SUPPORT Human Clinical

"Plasma AVP levels were low, and the posterior pituitary bright spot was absent on magnetic resonance imaging (MRI)."

Records the finding in molecularly confirmed hereditary disease, alongside the low hormone level it is taken to reflect.

PMID:38087160 SUPPORT Human Clinical

"its absence was shown in 70% of patients with AVP-D but also 39% of patients with primary polydipsia"

The numbers that make this a supporting rather than a pathognomonic sign, and the reason the entry does not model it as a phenotype.

AVP molecular genetic testing (PRESENT)

Sequencing AVP confirms the diagnosis, distinguishes the dominant from the recessive form, and is what makes presymptomatic testing of at-risk relatives possible - which matters because in the dominant form the biochemical abnormality lags the genotype by years. It does not predict when the disease will start or how severe it will be.

Show evidence (1 reference)

PMID:33433888 SUPPORT INDIRECT Human Clinical

"Five Portuguese families with autosomal dominant FNDI underwent sequencing of the AVP gene and the identified mutations were functionally characterized by in vitro studies."

Documents AVP sequencing as the diagnostic route in familial disease. The quote establishes the practice rather than asserting a diagnostic yield, hence directness INDIRECT.

📈

Progression

Infancy

In the dominant form there is characteristically nothing at birth. This is the single most informative feature of the natural history and it is what rules out simple haploinsufficiency: a dosage problem would be present from the start, whereas a slowly accumulating aggregate needs time. In the recessive P26L form, by contrast, disease is manifest in the neonatal period with hypernatraemic dehydration - which the authors of that series read as direct evidence against the gradual-destruction mechanism operating there.

Show evidence (1 reference)

PMID:19897608 SUPPORT Human Clinical

"This is the first description of autosomal recessive FNDI presenting in the neonatal period. The unusual early clinical and radiological (MRI) presentation argues against gradual destruction of AVP-secreting neurons as the pathophysiological mechanism."

Both halves of the claim in one sentence pair: the recessive form can present neonatally, and that timing is itself the argument that its mechanism is not progressive neuronal destruction.

Childhood

Polyuria and polydipsia appear, typically between one and six years of age, and deepen. Bedwetting and nocturia are often what brings the child to attention. The deficiency is frequently partial at this stage, so a water deprivation test can be equivocal in a child whose disease is unambiguous a few years later.

Show evidence (2 references)

PMID:19897608 SUPPORT Human Clinical

"Patients typically present between 1 and 6 years of age with polyuria and polydipsia."

Gives the age window for the typical dominant presentation.

PMID:10443701 SUPPORT Human Clinical

"The autosomal dominant form of familial neurohypophyseal diabetes insipidus (adFNDI) is a rare disease characterized by postnatal onset of polyuria and a deficient neurosecretion of the antidiuretic hormone, arginine vasopressin (AVP)."

States the postnatal - not congenital - onset that defines this phase.

Adulthood

The hormone deficit is by now severe and does not remit; desmopressin dependence is lifelong. Post-mortem series in affected adults show frank degeneration of the vasopressinergic hypothalamic nuclei, so what began as reversible cellular dysfunction has become structural loss. The clinical burden shifts from the polyuria itself, which desmopressin controls, to the hazards of treatment and of interrupted access to it: dilutional hyponatraemia on one side, hypernatraemic dehydration during illness, fasting or hospitalisation on the other.

Show evidence (2 references)

PMID:31785344 SUPPORT Human Clinical

"Post mortem studies in affected adults have shown cell degeneration in vasopressinergic hypothalamic nuclei."

The structural endpoint that distinguishes this phase from the earlier functional one.

PMID:38087160 SUPPORT Human Clinical

"Importantly, limited access to fluids or excessive fluid loss, for example, by non-availability or restricted intake, vomiting or diarrheal illnesses, unconsciousness, or acute concurrent illness, can lead to life-threatening dehydration"

Names the circumstances that make this a dangerous condition in adult life despite effective replacement therapy.

📊

Prevalence

Worldwide

Unknown Rare

No population-based prevalence estimate for the hereditary form was found in any cached source, and none is asserted here. Two things are citable and are recorded instead: the disorder is rare, and most central diabetes insipidus is acquired rather than genetic, so the familial share of an already uncommon syndrome is small. The RARE band is the coarsest honest statement the sources support; a numeric rate would be invented.

Show evidence (2 references)

PMID:31785344 SUPPORT Other

"This review focuses on the cellular and molecular aspects underlying familial neurohypophyseal diabetes insipidus (DI), a rare disorder that is usually transmitted in an autosomal-dominant fashion."

States that the familial disease is rare, which is the only occurrence claim the cached literature supports.

PMID:27156762 SUPPORT Other

"Although in most patients non-hereditary causes underlie the disorder, genetic forms have long been recognized and studied both in vivo and in vitro."

Establishes that the hereditary forms are a minority of neurohypophyseal diabetes insipidus overall, which is why the entry is scoped to them explicitly.

🐁

Animal Models

FNDI knock-in mouse (mutant neurophysin II)

The workhorse model of this disease and the source of nearly everything known about the timing of the mechanism. Heterozygous mice develop progressive polyuria as patients do, and the model has been used to separate the two arms of the cascade in time: aggregates accumulate and AVP transcription falls first, and neuronal death follows only later and only under osmotic load. Because the phenotype can be accelerated by intermittent water deprivation, the model also permits the neuron-loss endpoint to be reached in weeks rather than in the animal's whole lifespan.

Species

Mouse

Genotype

Heterozygous Avp knock-in encoding a mutant neurophysin II

Genes

AVP hgnc:894

Publication

PMID:19297548

Pathograph links

Endoplasmic Reticulum Retention and Fibrillar Aggregation recapitulates fidelity: high observes: molecular Aggregates form in the endoplasmic reticulum of supraoptic AVP neurons and grow in step with urine volume, so the model reproduces the retained aggregate in the correct cell type and in the correct temporal relation to the phenotype.

Limitations: The aggregates are not stained by antibodies to mutant neurophysin II, normal neurophysin II or AVP, so their exact composition in vivo is not established by the immunohistochemistry alone.

Readouts

Inclusion body size in supraoptic nucleus AVP cells

Direction: INCREASED

Interpretation: Morphological measure of the accumulating aggregate, tracked against urine volume in the same animals.

Show evidence (1 reference)

PMID:19297548 SUPPORT Model Organism

"the size of inclusion bodies gradually increased in parallel with the increases in urine volume"

Reports the measurement and its direction, and ties it quantitatively to the phenotype.

Show evidence (1 reference)

PMID:19297548 SUPPORT Model Organism

"At 12 mo, dilated ER filled with aggregates occupied the cytoplasm of AVP cells, while few aggregates were found in the nucleus."

Ultrastructural confirmation that the aggregate is where the mechanism says it should be, in a dilated ER of the affected neuron.

Vasopressin Neuron Secretory Dysfunction recapitulates fidelity: high observes: cellular AVP mRNA in the supraoptic nucleus falls while the AVP-expressing cell count is unchanged, which is the direct in-vivo demonstration that secretory failure precedes cell loss.

Readouts

AVP mRNA expression in supraoptic nucleus

Direction: DECREASED

Interpretation: In situ hybridisation measure of hormone-gene expression in the surviving neurons.

Show evidence (1 reference)

PMID:19297548 SUPPORT Model Organism

"Analyses with in situ hybridization revealed that expression of AVP mRNA was significantly decreased in the SON in the heterozygous mice compared with that in wild-type mice."

The measurement and its direction.

Magnocellular Vasopressin Neuron Loss partially recapitulates fidelity: moderate observes: organism Neuronal loss does occur, but only when the mutant neurons are driven by sustained osmotic demand; 30 to 40 per cent of AVP neurons are lost after twelve weeks of water deprivation.

Limitations: In unstressed animals the polyuria progresses substantially with no neuronal loss at all, so the timing of loss in this model is set by an experimental manipulation and cannot be read straight across to the human natural history. What the model shows is that loss is possible and demand-dependent, not when it happens in a patient.

Readouts

Surviving AVP neuron count after intermittent water deprivation

Direction: DECREASED

Interpretation: Cell counts after a defined osmotic challenge, the endpoint that establishes the degenerative arm of the mechanism.

Show evidence (1 reference)

PMID:29961215 SUPPORT Model Organism

"at which stage 30-40% of AVP neurons were lost"

The quantitative loss measured at the twelve-week water-deprivation endpoint.

Show evidence (1 reference)

PMID:19297548 SUPPORT Model Organism

"Counting cells expressing AVP mRNA in the SON indicated that polyuria had progressed substantially in the absence of neuronal loss."

The negative half of the same claim, and the reason this link is PARTIALLY_RECAPITULATES rather than RECAPITULATES: without an osmotic challenge the model's polyuria is not accompanied by cell loss.

Endoplasmic Reticulum Retention and Fibrillar Aggregation rescues fidelity: moderate observes: organism The chemical chaperone 4-phenylbutyrate reduced mutant protein accumulation in the ER of these mice, increased AVP release, cut urine volume and attenuated neuron loss under salt loading. This is the pharmacological test of the mechanism: relieving the ER burden improves both the hormone deficit and the degeneration, which is what a proteotoxicity model predicts and a haploinsufficiency model does not.

Limitations: A preclinical result in mice with no human trial in this disease; the entry records no corresponding treatment. It also does not establish which of the several downstream consequences of ER burden the benefit runs through.

Readouts

Urine volume on 4-phenylbutyrate

Direction: RESTORED

Interpretation: The organism-level output used to judge the rescue, alongside the molecular readout of reduced ER accumulation.

Show evidence (1 reference)

PMID:29886132 SUPPORT Model Organism

"Treatment with 4-PBA reduced mutant protein accumulation in the ER of FNDI mice and increased AVP release, leading to reduced urine volumes."

Reports the intervention and the direction of both the molecular and the physiological readout.

Show evidence (1 reference)

PMID:29886132 SUPPORT Model Organism

"Furthermore, AVP neuron loss under salt loading was attenuated by 4-PBA treatment."

Shows the rescue reaches the degenerative endpoint and not only the molecular one, which is what makes the ER burden causal rather than incidental.

Show evidence (1 reference)

PMID:19297548 SUPPORT Model Organism

"Here we analyzed knockin mice expressing mutant NPII that causes FNDI in humans. The heterozygous mice manifested progressive polyuria as do patients with FNDI."

Establishes the model, the human allele class it carries, and the cardinal phenotype it reproduces.

Cys67stop FNDI transgenic rat

An earlier transgenic rat expressing a truncating FNDI allele in vasopressin magnocellular neurons. Its contribution is the autophagy arm: it showed that the mutant protein accumulates in a swollen, distended ER that also holds wild-type endogenous vasopressin, and that the resulting vesicles are degradative autolysosomes rather than secretory structures.

Species

Rat

Genotype

Cys67stop mutant vasopressin transgene expressed in magnocellular neurons

Genes

AVP hgnc:894

Publication

PMID:12153465

Pathograph links

Endoplasmic Reticulum Stress and Autophagy Induction recapitulates fidelity: moderate observes: cellular Lysosomal and late-endosomal markers are upregulated specifically in the cells expressing the mutant transgene, and the aggregate-containing vesicles are immunoreactive for cathepsin D, endolyn and LAMP1.

Limitations: A transgene overexpressing a truncated allele rather than a knock-in of a patient mutation at the endogenous locus, so expression level and the species of retained protein both differ from the human situation. The readouts are marker immunoreactivity rather than flux measurements, so autophagic activity is inferred from the presence of autolysosomes.

Readouts

Lysosomal marker expression in transgene-expressing neurons

Direction: INCREASED

Interpretation: Cell-type-restricted upregulation of lysosomal markers, the evidence that autophagy is engaged by the mutant protein specifically.

Show evidence (1 reference)

PMID:12153465 SUPPORT Model Organism

"In addition, there is an up-regulation of lysosomal markers specifically in cells expressing Cys67stop."

The measurement, its direction and its restriction to the affected cells.

Show evidence (1 reference)

PMID:12153465 SUPPORT Model Organism

"We have now examined the expression of vesicular markers in our transgenic rats, and demonstrate that activation of autolysosomal processes is a consequence of the expression of Cys67stop."

Attests that this model is informative for the autophagy node specifically, and states the causal direction the authors claim - autolysosomal activation is a consequence of expressing the mutant.

Show evidence (1 reference)

PMID:12153465 SUPPORT Model Organism

"In rats expressing an FNDI mutant transgene (Cys67stop) in vasopressin magnocellular neurones, the mutant protein fails to enter the regulated secretory pathway, and accumulates in a swollen and distended endoplasmic reticulum (ER) that also contains wild-type, endogenous vasopressin."

Establishes the model and, in the same sentence, the co-retention of wild-type hormone that underlies the dominance of the human disease.

Sel1L-Hrd1 ERAD-deficient mouse

Not a model of the mutation, but a model of the mechanism's capacity limit, and for that reason one of the most informative animals in this literature. Removing the Sel1L-Hrd1 ERAD complex from vasopressin neurons that carry two normal AVP alleles is sufficient to produce ER retention, disulfide-bonded aggregation of proAVP and progressive diabetes insipidus. It shows that the disease phenotype follows from ERAD being overwhelmed, whichever side of the balance moves - a mutant client the machinery cannot handle, or intact clients with no machinery.

Species

Mouse

Genotype

Global or AVP-neuron-specific ablation of Sel1L-Hrd1 ER-associated degradation

Publication

PMID:28920920

Pathograph links

Endoplasmic Reticulum Retention and Fibrillar Aggregation recapitulates fidelity: moderate observes: molecular Reproduces the ER retention and intermolecular disulfide-bonded aggregation of proAVP that the human dominant alleles produce, and identifies protein disulfide isomerase activity as what drives the inappropriate cross-linking.

Limitations: The genetic lesion is in the quality-control machinery, not in AVP, so the model speaks to why retention is pathogenic and not to why a particular patient allele is retained. Loss of Sel1L-Hrd1 also removes ERAD for every other client in the neuron, so some of the phenotype may not run through proAVP at all.

Readouts

Disulfide-bonded proAVP aggregate formation

Direction: INCREASED

Interpretation: Biochemical measure of the aggregate species, in animals whose proAVP sequence is entirely normal.

Show evidence (1 reference)

PMID:28920920 SUPPORT Model Organism

"The inability to clear misfolded proAVP with highly reactive cysteine thiols in the absence of Sel1L-Hrd1 ERAD causes proAVP to accumulate and participate in inappropriate intermolecular disulfide-bonded aggregates, promoted by the enzymatic activity of protein disulfide isomerase (PDI)."

Reports the aggregate species and the chemistry that forms it, which is the same disulfide-linked fibrillar aggregate described in patients' alleles.

Show evidence (1 reference)

PMID:28920920 SUPPORT Model Organism

"Further, we show that proAVP is an endogenous substrate of Sel1L-Hrd1 ERAD."

Establishes that this model acts on the node's own substrate rather than on the neuron generically, which is what makes the link informative.

Show evidence (1 reference)

PMID:28920920 SUPPORT Model Organism

"Mice with global or AVP neuron-specific ablation of Se1L-Hrd1 ERAD progressively developed polyuria and polydipsia, characteristics of diabetes insipidus."

Establishes the model and the phenotype it produces. The abstract prints the gene as "Se1L" for Sel1L; the snippet reproduces the source exactly.

Brattleboro rat

The classical rodent model of central diabetes insipidus and the animal almost every physiological study of vasopressin replacement has used. It is recorded here for what it does not model. The lesion is a recessive frameshift that removes the normal stop codon and extends the C-terminus; the precursor is trapped in the ER, but the magnocellular neurons are preserved and there is no neurotoxicity, and the animals are affected only when homozygous. Every one of those is the opposite of the human dominant disease, so results obtained in this rat should not be read across to it.

Species

Rat

Genotype

Homozygous Avp single-guanine deletion in the neurophysin coding region (frameshift)

Publication

PMID:9756087

Pathograph links

Magnocellular Vasopressin Neuron Loss fails to recapitulate fidelity: low observes: cellular The Brattleboro rat retains its magnocellular vasopressin neurons. It has the hormone deficiency without the neurodegeneration, so it cannot be used to study the proteotoxic arm of the human disease and cannot be used to argue that the arm is unnecessary.

Limitations: Recessive rather than dominant, a frameshift with a read-through C-terminus rather than a missense or nonsense allele, and neurons preserved rather than lost. The source itself concludes that findings in this animal are only partially applicable to human hereditary disease.

Show evidence (2 references)

PMID:9756087 SUPPORT Model Organism

"However, in contrast to the recessive defect in the Brattleboro rat, in human CDI, neurotoxicity and denigration of the magnocellular neurons have been observed, and dominant inheritance occurs."

States the failure directly: neurotoxicity and magnocellular degeneration are human findings that this recessive rat does not show.

+ 1 more reference

Show evidence (1 reference)

PMID:9756087 SUPPORT Model Organism

"The mutated AVP gene precursor of Brattleboro rat has a deletion of a single base, guanine, in the neurophysin coding region that leads to a frameshift resulting in the loss of the normal stop codon."

Establishes the model and its causal allele, which is the basis for the comparison drawn below.

{ }

Source YAML

click to show

name: Neurohypophyseal Diabetes Insipidus
creation_date: '2026-09-05T18:20:00Z'
description: >-
  A hereditary deficiency of arginine vasopressin, transmitted in almost every
  family as an autosomal dominant trait, that presents in infancy or early
  childhood with hypotonic polyuria and compensatory polydipsia and worsens over
  years. The disease is not caused by loss of one working copy of AVP. A
  heterozygous mutation - almost always in the signal peptide or in the
  neurophysin II moiety of the prepro-vasopressin precursor - yields a
  folding-incompetent precursor that cannot leave the endoplasmic reticulum of
  the magnocellular neurons of the supraoptic and paraventricular nuclei. Part
  of it is cleared by ER-associated degradation; the rest forms disulfide-linked
  fibrillar aggregates that also trap the wild-type precursor made from the
  normal allele. The retained aggregate first disables hormone synthesis and
  secretion and then, over a longer timescale, kills the neuron by
  autophagy-associated death. That two-stage toxic gain of function is what
  explains the two features a haploinsufficiency model cannot: onset months to
  years after birth rather than at birth, and relentless progression despite one
  intact allele. Treatment is desmopressin, which replaces the missing hormone
  without touching the neuronal disease. A separate and much rarer autosomal
  recessive form exists, caused by homozygosity for AVP p.Pro26Leu, in which a
  weakly active hormone is synthesised, trafficked and secreted normally; there
  is no ER retention and no neuronal loss, and it is modelled here as a subtype
  precisely because its mechanism is the contrast case.
categories:
- Mendelian
- Protein Misfolding Disorder
- Disorder of the Neurohypophysis
classifications:
  harrisons_chapter:
  - classification_value: ENDOCRINOLOGY_METABOLISM
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
  mechanistic_category:
  - classification_value: proteotoxic disease
parents:
- central diabetes insipidus
- pituitary gland disorder
synonyms:
- familial neurohypophyseal diabetes insipidus
- autosomal dominant neurohypophyseal diabetes insipidus
- hereditary central diabetes insipidus
- arginine vasopressin deficiency
- vasopressin deficiency
- hereditary neurogenic diabetes insipidus
disease_term:
  preferred_term: neurohypophyseal diabetes insipidus
  term:
    id: MONDO:0007450
    label: neurohypophyseal diabetes insipidus
has_subtypes:
- name: AD FNDI
  display_name: Autosomal dominant familial neurohypophyseal diabetes insipidus
  description: >-
    The usual form, accounting for the great majority of families. A single
    heterozygous AVP allele encoding a folding-incompetent precursor is
    sufficient to cause disease, through retention and aggregation of the
    precursor in the endoplasmic reticulum of vasopressinergic neurons rather
    than through loss of hormone dosage. Onset is postnatal and the deficiency
    deepens with age.
  genes:
  - preferred_term: AVP
    term:
      id: hgnc:894
      label: AVP
  inheritance:
  - name: Autosomal dominant inheritance
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
    evidence:
    - reference: PMID:27156762
      reference_title: Genetic forms of neurohypophyseal diabetes insipidus.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "In most affected families, the disease is transmitted in an autosomal dominant manner, whereas autosomal recessive forms are much less frequent."
      explanation: Assigns dominant transmission to the majority of affected families, which
        is what makes this the default subtype.
  evidence:
  - reference: PMID:31785344
    reference_title: Role of protein aggregation and degradation in autosomal dominant neurohypophyseal
      diabetes insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The disease, manifesting in infancy or early childhood and gradually progressing in severity, is caused by fully penetrant heterozygous mutations in the gene encoding prepro-vasopressin-neurophysin II, the precursor of the antidiuretic hormone arginine vasopressin (AVP)."
    explanation: >-
      Establishes the dominant subtype as fully penetrant, heterozygous, of
      postnatal onset and progressive - the four features that separate it from
      the recessive subtype below.
- name: AR P26L
  display_name: Autosomal recessive familial neurohypophyseal diabetes insipidus (AVP p.Pro26Leu)
  description: >-
    A rare recessive form, reported in consanguineous Palestinian kindreds
    homozygous for AVP c.301C>T, replacing Pro26 of the precursor - Pro7 of the
    mature nonapeptide - with leucine. Heterozygous parents are unaffected. The
    mechanism is entirely different from the dominant form: the prohormone
    traffics through the secretory pathway normally and reaches the circulation,
    but the hormone it delivers binds the V2 receptor roughly thirtyfold less
    well, so circulating immunoreactive vasopressin is high while antidiuretic
    activity is low. This is a hormone-activity defect, not an ER storage
    disease, and there is no reason to expect vasopressinergic neurodegeneration
    in it.
  genes:
  - preferred_term: AVP
    term:
      id: hgnc:894
      label: AVP
  inheritance:
  - name: Autosomal recessive inheritance
    inheritance_term:
      preferred_term: Autosomal recessive inheritance
      term:
        id: HP:0000007
        label: Autosomal recessive inheritance
    evidence:
    - reference: PMID:10369876
      reference_title: Autosomal recessive familial neurohypophyseal diabetes insipidus with continued
        secretion of mutant weakly active vasopressin.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We studied an unusual Palestinian family consisting of asymptomatic first cousin parents and three children affected with neurohypophyseal diabetes insipidus, suggesting autosomal recessive inheritance."
      explanation: The pedigree that establishes recessive transmission for this subtype, with
        unaffected heterozygous parents.
  evidence:
  - reference: PMID:10369876
    reference_title: Autosomal recessive familial neurohypophyseal diabetes insipidus with continued
      secretion of mutant weakly active vasopressin.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All three affected children were homozygous and the parents heterozygous for a single novel mutation (C301->T) in exon 1, replacing Pro7 of mature AVP with Leu (Leu-AVP)."
    explanation: >-
      Establishes the recessive segregation and the causal allele, numbered here
      by residue of the mature hormone rather than of the precursor.
  - reference: PMID:10369876
    reference_title: Autosomal recessive familial neurohypophyseal diabetes insipidus with continued
      secretion of mutant weakly active vasopressin.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Leu-AVP was a weak agonist with approximately 30-fold reduced binding to the human V2 receptor."
    explanation: >-
      Quantifies the receptor-binding defect that makes this a hormone-activity
      subtype rather than a hormone-deficiency subtype.
  - reference: PMID:27156762
    reference_title: Genetic forms of neurohypophyseal diabetes insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Recessive transmission results from AVP with reduced biologic activity or the deletion of the locus."
    explanation: >-
      Confirms that recessive inheritance in this disease has a distinct
      mechanistic basis, and records the second recessive route - locus deletion
      - which is not covered by the p.Pro26Leu allele.
prevalence:
- population: Worldwide
  measure_type: UNKNOWN
  prevalence_class: RARE
  notes: >-
    No population-based prevalence estimate for the hereditary form was found in
    any cached source, and none is asserted here. Two things are citable and are
    recorded instead: the disorder is rare, and most central diabetes insipidus
    is acquired rather than genetic, so the familial share of an already
    uncommon syndrome is small. The RARE band is the coarsest honest statement
    the sources support; a numeric rate would be invented.
  evidence:
  - reference: PMID:31785344
    reference_title: Role of protein aggregation and degradation in autosomal dominant neurohypophyseal
      diabetes insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "This review focuses on the cellular and molecular aspects underlying familial neurohypophyseal diabetes insipidus (DI), a rare disorder that is usually transmitted in an autosomal-dominant fashion."
    explanation: States that the familial disease is rare, which is the only occurrence
      claim the cached literature supports.
  - reference: PMID:27156762
    reference_title: Genetic forms of neurohypophyseal diabetes insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Although in most patients non-hereditary causes underlie the disorder, genetic forms have long been recognized and studied both in vivo and in vitro."
    explanation: Establishes that the hereditary forms are a minority of neurohypophyseal
      diabetes insipidus overall, which is why the entry is scoped to them explicitly.
pathophysiology:
- name: Mutant Prepro-Vasopressin Misfolding
  description: >-
    The initiating lesion. A heterozygous point mutation in AVP - typically in
    the signal peptide or at a residue of the neurophysin II moiety that the
    precursor needs in order to fold and dimerise - yields a prepro-vasopressin
    that is folding incompetent. Signal-peptide alleles such as Ala(-1)Thr
    additionally prevent cleavage of the signal sequence, so an uncleaved
    23-kDa precursor accumulates. The lesion is in the precursor's ability to
    fold, not in the hormone it eventually encodes, which is why the mature
    nonapeptide is normal in these families and why a hormone-replacement drug
    works while the neuronal disease continues.
  biological_scale: MOLECULAR
  role: trigger
  mechanism_confidence: ESTABLISHED
  genes:
  - preferred_term: AVP
    term:
      id: hgnc:894
      label: AVP
  biological_processes:
  - preferred_term: protein folding in endoplasmic reticulum
    term:
      id: GO:0034975
      label: protein folding in endoplasmic reticulum
    modifier: ABNORMAL
  genetic_context:
    genes:
    - preferred_term: AVP
      term:
        id: hgnc:894
        label: AVP
    variant_origin: GERMLINE
    zygosity: HETEROZYGOUS
    functional_impact_category: DOMINANT_NEGATIVE
    description: >-
      The consequence of the variant is not loss of the encoded hormone's
      activity. The mutant precursor acquires a toxic aggregation property and,
      because it still dimerises with the product of the normal allele, drags
      wild-type precursor into the same ER-retained aggregate. That is a
      dominant-negative consequence layered on a toxic gain, and it is why the
      single normal allele does not rescue the phenotype. Contrast the recessive
      p.Pro26Leu allele, where the consequence really is reduced activity of the
      secreted hormone and heterozygotes are well.
  evidence:
  - reference: PMID:31785344
    reference_title: Role of protein aggregation and degradation in autosomal dominant neurohypophyseal
      diabetes insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Studies in cells expressing pathogenic mutants and knock-in rodent models have shown that the mutant precursors are folding incompetent and fail to exit the endoplasmic reticulum (ER), as occurs normally with proteins that have entered the regulated secretory pathway."
    explanation: States the folding-incompetence of the mutant precursor, which is the
      lesion this node models.
  - reference: PMID:10369876
    reference_title: Autosomal recessive familial neurohypophyseal diabetes insipidus with continued
      secretion of mutant weakly active vasopressin.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All published mutations affect the signal peptide or the neurophysin-II carrier protein and are presumed to interfere with processing of the preprohormone, leading to neuronal damage."
    explanation: Gives the position of the dominant alleles within the precursor, which is
      the structural regularity this node depends on.
  - reference: PMID:10085151
    reference_title: "Mutant vasopressin precursors that cause autosomal dominant neurohypophyseal diabetes insipidus retain dimerization and impair the secretion of wild-type proteins."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "An in vivo cross-linking reaction revealed homo- and heterodimer formation between WT and mutant precursors. Mutant precursors were also shown to impair intracellular trafficking of WT precursors from the endoplasmic reticulum to the Golgi apparatus."
    explanation: >-
      The experimental basis for `functional_impact_category: DOMINANT_NEGATIVE`
      on this node: the mutant precursor both dimerises with the wild-type
      product and blocks its ER-to-Golgi transit, which is why one normal allele
      does not rescue. The entry's `notes:` cited this paper for exactly that
      claim, so it now carries the evidence item rather than only a mention.
  - reference: PMID:10085151
    reference_title: "Mutant vasopressin precursors that cause autosomal dominant neurohypophyseal diabetes insipidus retain dimerization and impair the secretion of wild-type proteins."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "In addition to the cytotoxicity caused by mutant AVP precursors, the interaction between the WT and mutant precursors suggests that a dominant-negative mechanism may also contribute to the pathogenesis of familial neurohypophyseal diabetes insipidus."
    explanation: >-
      The authors' own reading, and deliberately hedged in the source ("suggests",
      "may also contribute"). Quoted with the hedge intact because the entry
      layers a dominant-negative consequence on a toxic gain rather than
      replacing one with the other.
  - reference: PMID:10443701
    reference_title: 'Clinical and molecular evidence of abnormal processing and trafficking of the
      vasopressin preprohormone in a large kindred with familial neurohypophyseal diabetes insipidus
      due to a signal peptide mutation.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Ala(- 1)Thr mutant cells produced 8-fold less AVP than wild-type cells and accumulated excessive amounts of 23-kDa NPII protein corresponding to uncleaved prepro-AVP-NPII."
    explanation: >-
      Shows the specific signal-peptide failure - the signal sequence is not
      cleaved, so uncleaved precursor accumulates and mature hormone output
      falls eightfold. Note the cached abstract prints the allele with a stray
      space as "Ala(- 1)Thr"; the snippet reproduces the source exactly.
  - reference: PMID:15356057
    reference_title: 'Differential cellular handling of defective arginine vasopressin (AVP) prohormones
      in cells expressing mutations of the AVP gene associated with autosomal dominant and recessive
      familial neurohypophyseal diabetes insipidus.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Our results provide an important negative control in support of the hypothesis that autosomal dominant inheritance of FNDI is caused by mutations in the AVP gene that alter amino acid residues important for folding and/or dimerization of the neurophysin II moiety of the AVP prohormone and subsequent transport from the endoplasmic reticulum."
    explanation: >-
      States the folding-and-dimerisation hypothesis for the neurophysin II
      alleles, and does so from a study whose recessive comparator is the
      negative control that makes the argument.
  downstream:
  - target: Endoplasmic Reticulum Retention and Fibrillar Aggregation
    causal_link_type: DIRECT
    description: >-
      A precursor that cannot fold cannot pass ER quality control, so it is
      retained rather than packaged into dense-core secretory granules.
    evidence:
    - reference: PMID:33433888
      reference_title: 'Familial neurohypophyseal diabetes insipidus: clinical, genetic and functional
        studies of novel mutations in the arginine vasopressin gene.'
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "In vitro transfection of neuronal cells with expression vectors containing each mutation showed that the mutations resulted in intracellular retention of the vasopressin prohormone."
      explanation: >-
        Directly links the mutations to intracellular retention of the
        prohormone, across five independent alleles spanning the signal peptide
        and neurophysin II, which is the step this edge asserts.

- name: Endoplasmic Reticulum Retention and Fibrillar Aggregation
  description: >-
    The retained precursor accumulates in the ER lumen of vasopressinergic
    magnocellular neurons. Some is retrotranslocated and destroyed by
    ER-associated degradation, but ERAD capacity is finite; the remainder
    self-associates into large disulfide-linked fibrillar aggregates. Crucially
    the aggregates are not pure mutant: wild-type precursor made from the normal
    allele is trapped in them, so one bad allele removes more than half the
    hormone-making capacity. In the knock-in mouse the aggregates are initially
    walled off in a sub-compartment of the ER and only later scatter through a
    dilated ER lumen, which is the ultrastructural correlate of the disease
    becoming progressive.
  biological_scale: MOLECULAR
  role: amplifier
  mechanism_confidence: ESTABLISHED
  conforms_to: "loss_of_proteostasis#Misfolded-Protein Aggregation"
  cell_types:
  - preferred_term: vasopressin-secreting magnocellular cell
    term:
      id: CL:4023109
      label: vasopressin-secreting magnocellular cell
  cellular_components:
  - preferred_term: endoplasmic reticulum
    term:
      id: GO:0005783
      label: endoplasmic reticulum
  biological_processes:
  - preferred_term: ERAD pathway
    term:
      id: GO:0036503
      label: ERAD pathway
    modifier: INCREASED
  locations:
  - preferred_term: supraoptic nucleus
    term:
      id: UBERON:0001929
      label: supraoptic nucleus
  - preferred_term: paraventricular nucleus of hypothalamus
    term:
      id: UBERON:0001930
      label: paraventricular nucleus of hypothalamus
  evidence:
  - reference: PMID:31588537
    reference_title: Hereditary Neurohypophyseal Diabetes Insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Current data show that retained mutants fail to be eliminated by the cell's quality control system and accumulate in fibrillar aggregations within the ER."
    explanation: States both halves of this node - quality-control failure and fibrillar
      aggregation in the ER.
  - reference: PMID:31785344
    reference_title: Role of protein aggregation and degradation in autosomal dominant neurohypophyseal
      diabetes insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "A portion of these mutants is eliminated via ER-associated degradation (ERAD) by proteasomes after retrotranslocation to the cytosol. Another portion forms large disulfide-linked fibrillar aggregates within the ER, in which wild-type precursor is trapped."
    explanation: >-
      Gives the two fates of the retained precursor and, decisively for the
      dominance of the disease, records that wild-type precursor is trapped in
      the aggregate.
  - reference: PMID:29961215
    reference_title: A novel mechanism of autophagy-associated cell death of vasopressin neurons in
      familial neurohypophysial diabetes insipidus.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Electron microscopic analyses revealed that aggregates were confined to a sub-compartment of the endoplasmic reticulum (ER), ER-associated compartment (ERAC), in AVP neurons of FNDI mice under normal conditions."
    explanation: Establishes the in-vivo ultrastructure of the aggregate in the neuron the
      disease actually affects, and its initial containment.
  - reference: PMID:34232487
    reference_title: Functional analyses of three different mutations in the AVP-NPII gene causing
      familial neurohypophyseal diabetes insipidus.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Fluorescence imaging studies showed that a substantial portion of the mutant p.G45C and p.G88V AVP-NPII precursors appeared to be located in the endoplasmic reticulum (ER), whereas 207_209delGGC and WT AVP-NPII precursors were distributed throughout the cytoplasm."
    explanation: >-
      Independent allele-level confirmation of ER localisation, and a useful
      negative control: an in-frame deletion that did not retain traffic
      normally, so retention is a property of particular alleles rather than of
      any AVP change.
  - reference: PMID:28920920
    reference_title: ER-associated degradation is required for vasopressin prohormone processing and
      systemic water homeostasis.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Mechanistically, we found that ERAD deficiency causes marked ER retention and aggregation of a large proportion of all proAVP protein."
    explanation: >-
      The converse experiment, and the strongest evidence that ERAD capacity is
      what stands between a vasopressin neuron and this node: remove the
      Sel1L-Hrd1 machinery and even entirely wild-type proAVP is retained and
      aggregates. It establishes ERAD saturation as a sufficient cause of the
      aggregation step rather than an incidental accompaniment of it.
  downstream:
  - target: Vasopressin Neuron Secretory Dysfunction
    causal_link_type: DIRECT
    description: >-
      Aggregate accumulation disables hormone production and release before any
      cell is lost, which is the step that makes polyuria precede
      neurodegeneration.
    evidence:
    - reference: PMID:19297548
      reference_title: Progressive polyuria without vasopressin neuron loss in a mouse model for familial
        neurohypophysial diabetes insipidus.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "These data suggest that cell death is not the primary cause of polyuria in FNDI, and that the aggregates accumulated in the ER might be involved in the dysfunction of AVP neurons that lead to the progressive polyuria."
      explanation: >-
        The authors' own statement of this edge - the aggregate causes neuronal
        dysfunction, and that dysfunction rather than cell death is what
        produces the polyuria.
  - target: Endoplasmic Reticulum Stress and Autophagy Induction
    causal_link_type: DIRECT
    description: >-
      Once aggregates exceed the ER-associated compartment that contains them
      and spill into a dilating ER lumen, the cell turns to autophagy.
    evidence:
    - reference: PMID:12153465
      reference_title: Autophagy in hypothalamic neurones of rats expressing a familial neurohypophysial
        diabetes insipidus transgene.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "These data support the proposal that Cys67stop mutant protein aggregates within the ER, which is targeted for lysosomal degradation by autophagy."
      explanation: >-
        States the causal step this edge asserts, in vivo, in the vasopressin
        magnocellular neurons of a transgenic rat.

- name: Endoplasmic Reticulum Stress and Autophagy Induction
  description: >-
    The aggregate burden imposes sustained stress on the ER of the vasopressin
    neuron and drives autophagy. Phagophores form around the aggregate-laden ER
    and engulf it. This is initially a protective response: it is the cell's
    attempt to clear what ERAD could not. It becomes destructive because it does
    not stop - continuous autophagy strips the neuron of organelles, including
    the ER itself.
  biological_scale: CELLULAR
  role: amplifier
  mechanism_confidence: ESTABLISHED
  cell_types:
  - preferred_term: vasopressin-secreting magnocellular cell
    term:
      id: CL:4023109
      label: vasopressin-secreting magnocellular cell
  biological_processes:
  - preferred_term: response to endoplasmic reticulum stress
    term:
      id: GO:0034976
      label: response to endoplasmic reticulum stress
    modifier: INCREASED
  - preferred_term: macroautophagy
    term:
      id: GO:0016236
      label: macroautophagy
    modifier: INCREASED
  evidence:
  - reference: PMID:41045372
    reference_title: Phagophores originate from endoplasmic reticulum membranes in vasopressin neurons
      in a mouse model of familial neurohypophysial diabetes insipidus.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Three-dimensional analysis revealed that phagophores enveloped aggregates located within the dilated ER. Serial imaging further demonstrated a physical connection between these phagophores and intact ER membranes."
    explanation: >-
      Three-dimensional electron microscopy of the affected neuron showing the
      autophagic machinery engaging the aggregate-containing ER directly, and
      forming from ER membrane rather than arriving from elsewhere.
  - reference: PMID:12153465
    reference_title: Autophagy in hypothalamic neurones of rats expressing a familial neurohypophysial
      diabetes insipidus transgene.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Swollen vesicles containing Cys67stop are immunoreactive for cathepsin D (a lysosomal protease), endolyn (a marker of late endosomes) and lysosomal associated membrane protein 1, suggesting that they may be degradative autolysosomes."
    explanation: Identifies the vesicles that accumulate around the mutant protein as
      degradative autolysosomes, which is the autophagic arm of this node.
  downstream:
  - target: Magnocellular Vasopressin Neuron Loss
    causal_link_type: DIRECT
    description: >-
      Unrelenting autophagy consumes the neuron's organelles and ends in cell
      death rather than in clearance.
    evidence:
    - reference: PMID:29961215
      reference_title: A novel mechanism of autophagy-associated cell death of vasopressin neurons in
        familial neurohypophysial diabetes insipidus.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Our data demonstrated that although autophagy should primarily be a protective mechanism, continuous autophagy leads to gradual loss of organelles including ER, resulting in autophagy-associated cell death of AVP neurons in FNDI mice."
      explanation: >-
        States the edge and names the death mode, and is careful about the
        direction: autophagy is protective first and lethal only when it
        persists.
  - target: Vasopressin Neuron Secretory Dysfunction
    causal_link_type: DIRECT
    description: >-
      A second, transcript-level route from the same stress. ER stress shortens
      the poly(A) tail of AVP mRNA and lowers its expression, which throttles
      the supply of new precursor. The cell is reducing the unfolded-protein
      load it has to handle, and the price is hormone output.
    evidence:
    - reference: PMID:24121282
      reference_title: 'Endoplasmic reticulum stress in vasopressin neurons of familial diabetes insipidus
        model mice: aggregate formation and mRNA poly(A) tail shortening.'
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Incubation of hypothalamic explants of wild-type mice with ER stressors caused shortening of the poly(A) tail length of AVP mRNA, accompanied by decreases in the expression."
      explanation: >-
        Establishes the direction of this edge experimentally rather than by
        correlation: applying ER stress to wild-type tissue reproduces the
        transcript change seen in the mutant animals.

- name: Vasopressin Neuron Secretory Dysfunction
  description: >-
    Before any neuron dies, the surviving neurons stop working. AVP mRNA in the
    supraoptic nucleus falls, mature hormone output collapses, and the regulated
    secretory pathway is starved of cargo because the precursor never reaches
    the trans-Golgi network. This node is the reason the disease is progressive
    from an early age and yet compatible with a normal neuron count for a long
    time, and it is separated from the neuron-loss node deliberately: the mouse
    data show polyuria advancing substantially while the AVP-expressing cell
    count is still intact.
  biological_scale: CELLULAR
  role: effector
  mechanism_confidence: ESTABLISHED
  cell_types:
  - preferred_term: vasopressin-secreting magnocellular cell
    term:
      id: CL:4023109
      label: vasopressin-secreting magnocellular cell
  biological_processes:
  - preferred_term: vasopressin secretion
    term:
      id: GO:0030103
      label: vasopressin secretion
    modifier: DECREASED
  evidence:
  - reference: PMID:19297548
    reference_title: Progressive polyuria without vasopressin neuron loss in a mouse model for familial
      neurohypophysial diabetes insipidus.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Analyses with in situ hybridization revealed that expression of AVP mRNA was significantly decreased in the SON in the heterozygous mice compared with that in wild-type mice. Counting cells expressing AVP mRNA in the SON indicated that polyuria had progressed substantially in the absence of neuronal loss."
    explanation: >-
      The direct evidence for this node as a distinct step - transcript and
      function fall while the cells are still there and still counted.
  - reference: PMID:10443701
    reference_title: 'Clinical and molecular evidence of abnormal processing and trafficking of the
      vasopressin preprohormone in a large kindred with familial neurohypophyseal diabetes insipidus
      due to a signal peptide mutation.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The clinical studies showed a severe progressive deficiency of plasma and urinary AVP that manifested during childhood."
    explanation: The human counterpart of the same claim, measured as hormone output in an
      affected kindred rather than as transcript in a mouse.
  downstream:
  - target: Progressive Arginine Vasopressin Deficiency
    causal_link_type: DIRECT
    description: >-
      Neurons that cannot transcribe, process or release the hormone deliver
      less of it to the circulation, and do so increasingly over time.
    evidence:
    - reference: PMID:24121282
      reference_title: 'Endoplasmic reticulum stress in vasopressin neurons of familial diabetes insipidus
        model mice: aggregate formation and mRNA poly(A) tail shortening.'
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Despite polyuria, which could potentially induce dehydration, AVP mRNA expression was decreased in the supraoptic nucleus, and the AVP mRNA poly(A) tail length was shortened in FNDI mice compared with wild-type mice."
      explanation: >-
        Demonstrates the failure of hormone supply against the strongest
        possible physiological stimulus to increase it - the animals are
        polyuric and dehydrating, and expression still falls.

- name: Magnocellular Vasopressin Neuron Loss
  description: >-
    The end state of the proteotoxic cascade. Vasopressinergic magnocellular
    neurons of the supraoptic and paraventricular nuclei degenerate, which is
    what post-mortem examination of affected adults shows and what makes this
    disease, in Rutishauser's phrase, a neurodegeneration confined to one
    neuronal population. Loss is not all-or-nothing and is accelerated by
    osmotic demand: in the knock-in mouse, sustained water deprivation - which
    forces the mutant neurons to work - destroys 30 to 40 per cent of them
    within twelve weeks. Oxytocin magnocellular neurons in the same nuclei are
    spared, because they do not make the mutant cargo.
  biological_scale: CELLULAR
  role: consequence
  mechanism_confidence: ESTABLISHED
  conforms_to: "loss_of_proteostasis#Proteotoxic Cell Dysfunction and Neurodegeneration"
  cell_types:
  - preferred_term: vasopressin-secreting magnocellular cell
    term:
      id: CL:4023109
      label: vasopressin-secreting magnocellular cell
  biological_processes:
  - preferred_term: neuron apoptotic process
    term:
      id: GO:0051402
      label: neuron apoptotic process
    modifier: INCREASED
  locations:
  - preferred_term: supraoptic nucleus
    term:
      id: UBERON:0001929
      label: supraoptic nucleus
  - preferred_term: paraventricular nucleus of hypothalamus
    term:
      id: UBERON:0001930
      label: paraventricular nucleus of hypothalamus
  evidence:
  - reference: PMID:31785344
    reference_title: Role of protein aggregation and degradation in autosomal dominant neurohypophyseal
      diabetes insipidus.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Post mortem studies in affected adults have shown cell degeneration in vasopressinergic hypothalamic nuclei."
    explanation: The human neuropathological observation on which the whole neurotoxicity
      model was originally built.
  - reference: PMID:31588537
    reference_title: Hereditary Neurohypophyseal Diabetes Insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Autosomal dominant neurohypophyseal DI may thus be viewed as a neurodegenerative disease confined to vasopressinergic neurons."
    explanation: States the framing this node adopts, including the cell-type restriction
      that distinguishes it from a general proteinopathy.
  - reference: PMID:29961215
    reference_title: A novel mechanism of autophagy-associated cell death of vasopressin neurons in
      familial neurohypophysial diabetes insipidus.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Furthermore, the cytoplasm was entirely occupied with large vacuoles in AVP neurons of FNDI mice subjected to water deprivation for 12 weeks, at which stage 30-40% of AVP neurons were lost."
    explanation: Quantifies the loss in vivo and ties its rate to osmotic demand on the
      mutant neurons.
  downstream:
  - target: Progressive Arginine Vasopressin Deficiency
    causal_link_type: DIRECT
    description: >-
      Neurons that have died cannot be recruited, so this arm makes the
      deficiency irreversible where the secretory-dysfunction arm alone might
      not be.

- name: Secreted Weakly Active Vasopressin
  description: >-
    The recessive contrast mechanism, present only in the AR P26L subtype. The
    p.Pro26Leu precursor is not folding incompetent: it moves through the
    secretory pathway, is packaged into granules in the cell processes and is
    released, so there is no ER retention, no aggregate and no proteotoxic
    threat to the neuron. What reaches the circulation is a poor V2 receptor
    agonist. Immunoreactive vasopressin in serum is therefore high, not low -
    the opposite of the dominant disease - while antidiuresis fails all the
    same. This node is included because the recessive form is otherwise easy to
    read as a milder version of the same disease, and it is not.
  biological_scale: MOLECULAR
  role: trigger
  mechanism_confidence: ESTABLISHED
  subtypes:
  - AR P26L
  genes:
  - preferred_term: AVP
    term:
      id: hgnc:894
      label: AVP
  evidence:
  - reference: PMID:15356057
    reference_title: 'Differential cellular handling of defective arginine vasopressin (AVP) prohormones
      in cells expressing mutations of the AVP gene associated with autosomal dominant and recessive
      familial neurohypophyseal diabetes insipidus.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Confocal laser scanning microscopy showed accumulation of the Y21H prohormone in the endoplasmic reticulum, whereas the P26L prohormone and/or processed products were localized in secretory granules in the cellular processes."
    explanation: >-
      Side-by-side demonstration in one experiment that the dominant allele is
      ER-retained and the recessive one is not, which is the whole basis for
      modelling them as different mechanisms.
  - reference: PMID:15356057
    reference_title: 'Differential cellular handling of defective arginine vasopressin (AVP) prohormones
      in cells expressing mutations of the AVP gene associated with autosomal dominant and recessive
      familial neurohypophyseal diabetes insipidus.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Thus, the recessive mutation does not seem to affect the intracellular trafficking but rather the final processing of the prohormone."
    explanation: The authors' summary of where the recessive defect lies, which is downstream
      of everything the dominant mechanism turns on.
  - reference: PMID:10369876
    reference_title: Autosomal recessive familial neurohypophyseal diabetes insipidus with continued
      secretion of mutant weakly active vasopressin.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Measured by radioimmunoassay with a synthetic Leu-AVP standard, serum Leu-AVP levels were elevated in all three children and further increased during water deprivation to as high as 30 times normal."
    explanation: >-
      Establishes in patients that the mutant hormone is made, secreted and
      osmotically regulated - so the deficiency in this subtype is of hormone
      action, not of hormone supply.
  downstream:
  - target: Impaired Renal Free Water Reabsorption
    causal_link_type: DIRECT
    description: >-
      A weak V2 agonist circulating at high concentration still fails to
      generate an adequate antidiuretic signal at the collecting duct.
    evidence:
    - reference: PMID:31588537
      reference_title: Hereditary Neurohypophyseal Diabetes Insipidus.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Symptoms result from the lack of hormone, or from the inability of mutant AVP to activate its renal receptor, and respond to treatment with desmopressin (DDAVP)."
      explanation: >-
        Names both routes to the same renal endpoint and assigns the second one
        - receptor activation failure - to exactly this situation.

- name: Progressive Arginine Vasopressin Deficiency
  description: >-
    The systemic consequence: circulating arginine vasopressin falls below what
    is needed to concentrate urine, and continues to fall over years as more
    neurons become dysfunctional and then die. Partial deficiency is common
    early, so the water deprivation test can be equivocal in a child who will
    later have unmistakable disease. Osmoregulated thirst is intact, which is
    what keeps most patients in water balance and turns the deficiency into a
    drinking problem rather than a hypernatraemia problem.
  biological_scale: ORGANISM
  role: effector
  mechanism_confidence: ESTABLISHED
  chemical_entities:
  - preferred_term: arginine vasopressin
    term:
      id: CHEBI:34543
      label: argipressin
    modifier: DECREASED
  evidence:
  - reference: PMID:31588537
    reference_title: Hereditary Neurohypophyseal Diabetes Insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Dominant mutations cause retention of the hormone precursor in the endoplasmic reticulum (ER) of vasopressinergic neurons in the hypothalamus, resulting in cellular dysfunction and eventually neuronal death."
    explanation: Traces the chain from ER retention through dysfunction to death, the two
      upstream arms that converge on this node.
  - reference: PMID:29961215
    reference_title: A novel mechanism of autophagy-associated cell death of vasopressin neurons in
      familial neurohypophysial diabetes insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Familial neurohypophysial diabetes insipidus (FNDI), characterized by delayed-onset progressive polyuria and loss of arginine vasopressin (AVP) neuron, is an autosomal dominant disorder caused by AVP gene mutations."
    explanation: States the delayed onset and progressive character that this node is
      responsible for, as opposed to a congenital fixed deficit.
  downstream:
  - target: Impaired Renal Free Water Reabsorption
    causal_link_type: DIRECT
    description: >-
      The endocrine-to-renal step. Circulating vasopressin is the ligand for the
      V2 receptor on the collecting duct principal cell, and without it the
      aquaporin-2 trafficking that makes the duct water-permeable does not
      happen.
    evidence:
    - reference: PMID:29421628
      reference_title: '[Nephrogenic diabetes insipidus].'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Binding of AVP to the arginine-vasopressin receptor type-2 in the basolateral membrane leads to translocation of aquaporin-2 water channels to the apical membrane of the principal cells of the collecting duct, inducing water permeability of the membrane."
      explanation: >-
        Gives the molecular mechanism of this edge in the forward direction.
        The paper is about the nephrogenic disease, where the same axis fails at
        the receptor rather than at the ligand, so the physiology it states
        supports this edge by inference rather than by studying it.
      directness: INDIRECT

- name: Impaired Renal Free Water Reabsorption
  description: >-
    Without an adequate vasopressin signal at the V2 receptor of the collecting
    duct principal cell, aquaporin-2 is not inserted into the apical membrane,
    the duct stays water-impermeable and the osmotic gradient of the medulla
    cannot be used. Large volumes of maximally dilute urine are lost. Everything
    clinical in this disease follows from here.
  biological_scale: TISSUE
  role: effector
  mechanism_confidence: ESTABLISHED
  biological_processes:
  - preferred_term: renal water absorption
    term:
      id: GO:0070295
      label: renal water absorption
    modifier: DECREASED
  locations:
  - preferred_term: collecting duct of renal tubule
    term:
      id: UBERON:0001232
      label: collecting duct of renal tubule
  evidence:
  - reference: PMID:27156762
    reference_title: Genetic forms of neurohypophyseal diabetes insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Neurohypophyseal diabetes insipidus is characterized by polyuria and polydipsia owing to partial or complete deficiency of the antidiuretic hormone, arginine vasopressin (AVP)."
    explanation: States that the renal water-handling failure and its clinical expression
      follow from vasopressin deficiency, which is the step this node carries.
  downstream:
  - target: Polyuria
    causal_link_type: DIRECT
    description: >-
      Water that is not reabsorbed in the collecting duct is excreted, so the
      urine volume is large and its osmolality low.
    evidence:
    - reference: PMID:29421628
      reference_title: '[Nephrogenic diabetes insipidus].'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "This results in water reabsorption in the collecting duct of the nephron following an osmotic gradient."
      explanation: >-
        States the reabsorption step whose failure produces the polyuria. The
        quote gives the normal physiology, so it supports the edge by
        inference rather than by measuring it in this disease.
      directness: INDIRECT
  - target: Hyposthenuria
    causal_link_type: DIRECT
    description: >-
      The same failure of collecting-duct water permeability that raises the
      volume lowers the concentration, so the two renal phenotypes are one
      event measured two ways.
  - target: Nocturia
    causal_link_type: DIRECT
    description: >-
      Antidiuresis fails around the clock, so the obligate water loss continues
      overnight when drinking has stopped.
  - target: Polydipsia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Urinary water loss raises plasma osmolality, and intact osmoreceptor-driven
      thirst then produces the compensatory drinking.
  - target: Hypernatremic Dehydration
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Only when thirst cannot be acted on - in an infant, or in anyone without
      free access to water - does the water loss become a sodium and volume
      emergency.
phenotypes:
- category: Renal
  name: Polyuria
  frequency: OBLIGATE
  diagnostic: true
  description: >-
    Excretion of large volumes of hypotonic urine, conventionally more than
    50 mL per kg body weight per 24 hours. It is the presenting complaint and the
    phenotype that defines the polyuria-polydipsia syndrome this disease belongs
    to. It appears postnatally rather than at birth, and worsens over childhood.
  phenotype_term:
    preferred_term: Polyuria
    term:
      id: HP:0000103
      label: Polyuria
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The polyuria-polydipsia syndrome is characterized by a high urinary output of more than 50 ml per kg body weight per 24 h, accompanied by polydipsia of more than 3 L a day"
    explanation: Gives the quantitative threshold used clinically to call the urine output
      polyuric, and pairs it with the polydipsia phenotype below.
  - reference: PMID:19897608
    reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
      infancy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients typically present between 1 and 6 years of age with polyuria and polydipsia."
    explanation: Establishes polyuria as the typical presenting phenotype and gives the age
      window, which is the postnatal-onset claim this entry rests on.
- category: Renal
  name: Polydipsia
  frequency: OBLIGATE
  description: >-
    Compensatory drinking driven by intact osmoregulated thirst. It is what
    keeps most patients eunatraemic despite losing many litres a day, and it is
    also why the disease is survivable at all before diagnosis. Loss of free
    access to water converts a manageable disorder into a dangerous one within
    hours.
  phenotype_term:
    preferred_term: Polydipsia
    term:
      id: HP:0001959
      label: Polydipsia
  evidence:
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In most patients, osmoregulated thirst perception is intact and adequate fluid intake compensates for urinary water loss"
    explanation: Establishes that the polydipsia is intact-thirst compensation rather than a
      primary drinking disorder, which is the distinction the differential turns on.
  - reference: PMID:33433888
    reference_title: 'Familial neurohypophyseal diabetes insipidus: clinical, genetic and functional
      studies of novel mutations in the arginine vasopressin gene.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients showed progressive symptoms of polyuria and polydipsia, but with wide variability in severity and age at onset."
    explanation: Documents the paired phenotype across five kindreds and records the
      variability in onset and severity that complicates family screening.
- category: Renal
  name: Hyposthenuria
  frequency: VERY_FREQUENT
  diagnostic: true
  description: >-
    Persistently dilute urine. Urine osmolality stays far below plasma even when
    plasma osmolality is high, which is the finding that separates this disease
    from an osmotic diuresis and is the measurement the water deprivation test
    is built around.
  phenotype_term:
    preferred_term: Hyposthenuria
    term:
      id: HP:0003158
      label: Hyposthenuria
  evidence:
  - reference: PMID:19897608
    reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
      infancy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients developed hypernatremia (154-163 mmol/l) and serum hyperosmolality (>320 mOsm/kg), while urine osmolality remained between 73 and 229 mOsm/kg."
    explanation: >-
      The defining dissociation, with numbers: serum hyperosmolality above
      320 mOsm/kg alongside urine osmolality as low as 73 mOsm/kg.
- category: Metabolic
  name: Hypernatremic Dehydration
  frequency: OCCASIONAL
  description: >-
    Hypernatraemia with serum hyperosmolality, seen when water intake cannot
    match the loss. It is the presentation of the recessive infantile form, and
    in the dominant form it is the complication of illness, fasting,
    hospitalisation or any other interruption of drinking rather than a routine
    feature.
  phenotype_term:
    preferred_term: Hypernatremic dehydration
    term:
      id: HP:0004906
      label: Hypernatremic dehydration
  evidence:
  - reference: PMID:19897608
    reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
      infancy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients developed hypernatremia (154-163 mmol/l) and serum hyperosmolality (>320 mOsm/kg)"
    explanation: Documents the hypernatraemic presentation with measured sodium and osmolality
      in infants who could not drink to compensate.
- category: Constitutional
  name: Failure to Thrive in Infancy
  frequency: OCCASIONAL
  description: >-
    In infants, who cannot ask for water, the disease presents not as thirst but
    as poor growth with vomiting, irritability and unexplained fever - a
    presentation easily attributed to feeding difficulty or infection. This is
    the recorded presentation of the recessive P26L kindred and is the reason
    the recessive form is diagnosed so much earlier than the dominant one.
  phenotype_term:
    preferred_term: Failure to thrive in infancy
    term:
      id: HP:0001531
      label: Failure to thrive in infancy
  evidence:
  - reference: PMID:19897608
    reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
      infancy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Three Palestinian cousins presented with failure to thrive, vomiting, irritability, and fever."
    explanation: Records the infantile presentation directly, including the non-specific
      symptoms that accompany it.
- category: Constitutional
  name: Vomiting
  frequency: OCCASIONAL
  description: >-
    Reported as part of the infantile presentation, alongside failure to thrive
    and irritability. It is not a feature of the disease in older children and
    adults, where thirst dominates the picture.
  phenotype_term:
    preferred_term: Vomiting
    term:
      id: HP:0002013
      label: Vomiting
  evidence:
  - reference: PMID:19897608
    reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
      infancy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Three Palestinian cousins presented with failure to thrive, vomiting, irritability, and fever."
    explanation: Names vomiting as one of the presenting features in affected infants.
- category: Renal
  name: Nocturia
  frequency: FREQUENT
  description: >-
    Night-time urination, which is usually the first symptom desmopressin is
    prescribed to control and therefore the practical endpoint of initial
    dosing. Its prominence follows from the fact that antidiuresis fails around
    the clock while drinking is voluntary and daytime.
  phenotype_term:
    preferred_term: Nocturia
    term:
      id: HP:0000017
      label: Nocturia
    temporality: NOCTURNAL
  evidence:
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The initial treatment aim is to reduce nocturia, and therefore, the first desmopressin dose is usually given at bedtime, and if needed, a daytime dose is added."
    explanation: >-
      Establishes nocturia as a recognised and clinically targeted manifestation.
      The quote supports it through the treatment aim rather than by naming a
      frequency, hence directness INDIRECT.
    directness: INDIRECT
biochemical:
- name: Plasma arginine vasopressin
  presence: Decreased
  context: >-
    The direct measure of the deficiency in the dominant form. It falls
    progressively over childhood in parallel with urinary AVP. Note the sign
    reverses in the recessive P26L subtype, where immunoreactive hormone is
    high because a poorly active peptide is still being secreted - so a normal
    or elevated result does not exclude hereditary disease until the subtype is
    known. In practice AVP itself is rarely measured now; copeptin has replaced
    it because AVP is unstable and largely platelet-bound.
  biomarker_term:
    preferred_term: arginine vasopressin
    term:
      id: NCIT:C2285
      label: Arginine-Vasopressin
  readouts:
  - target: Progressive Arginine Vasopressin Deficiency
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Directly reports the circulating hormone concentration that this node
      is about.
    evidence:
    - reference: PMID:10443701
      reference_title: 'Clinical and molecular evidence of abnormal processing and trafficking of the
        vasopressin preprohormone in a large kindred with familial neurohypophyseal diabetes insipidus
        due to a signal peptide mutation.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The clinical studies showed a severe progressive deficiency of plasma and urinary AVP that manifested during childhood."
      explanation: Reports the analyte, its direction and its progressive course in an
        affected kindred.
  evidence:
  - reference: PMID:19897608
    reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
      infancy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Plasma AVP levels were low, and the posterior pituitary bright spot was absent on magnetic resonance imaging (MRI)."
    explanation: Documents low plasma AVP measured in affected patients, together with the
      imaging correlate.
- name: Plasma copeptin
  presence: Decreased
  context: >-
    Copeptin is the C-terminal glycopeptide of the same prepro-vasopressin
    precursor, released in equimolar amounts with the hormone but far more
    stable, and it has displaced AVP as the assay of record. A stimulated
    copeptin that stays low is the diagnostic finding; a high unstimulated
    copeptin instead points to vasopressin resistance. Copeptin is also one of
    the two domains of the precursor that confers aggregation capacity, so in
    this disease the marker and the toxic species are parts of one molecule.
  biomarker_term:
    preferred_term: copeptin (C-terminal pro-vasopressin)
    term:
      id: NCIT:C26089
      label: Vasopressin-Neurophysin 2-Copeptin
  readouts:
  - target: Progressive Arginine Vasopressin Deficiency
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: A surrogate for vasopressin secretion, measured after osmotic stimulation
      so that a low value means failure to secrete rather than absence of a stimulus.
    evidence:
    - reference: PMID:30067922
      reference_title: A Copeptin-Based Approach in the Diagnosis of Diabetes Insipidus.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "In the latter test, plasma copeptin was measured when the plasma sodium level had increased to at least 150 mmol per liter after infusion of hypertonic saline."
      explanation: Specifies how the readout is obtained - the osmotic stimulus that makes a
        low copeptin interpretable.
  evidence:
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Using the pre-defined copeptin cut-off of ≤ 4.9 mmol/L, patients with AVP-D were reliably distinguished from patients with primary polydipsia with a diagnostic accuracy of 97%."
    explanation: >-
      Gives the operating threshold and its accuracy. Two things about this
      quote only make sense against the diagnosis section. The review prints the
      unit as mmol/L where the primary trial reports pmol per litre; the snippet
      quotes the cached source exactly and the correct unit is picked up from
      PMID:30067922 there. And its 97% is the review's rounding of the same
      measurement that section reports as 96.5% - same trial, same test, same
      4.9 cutoff - not a second analysis. The cached record of PMID:30067922 is
      abstract-only; it gives 96.5% as the test's overall accuracy, and 95.2%
      for the partial-central-DI-versus-primary-polydipsia subgroup, and no 97%.
      So the reading rests on 96.5% being the only figure in that record which
      97% could be a rounding of, not on a search of the full paper.
  - reference: PMID:31785344
    reference_title: Role of protein aggregation and degradation in autosomal dominant neurohypophyseal
      diabetes insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Aggregation capacity is independently conferred by two domains of the prohormone, namely the AVP moiety and the C-terminal glycopeptide (copeptin)."
    explanation: Records that copeptin is one of the aggregation-competent domains, which is
      why this marker is mechanistically as well as diagnostically interesting here.
- name: Urine osmolality
  presence: Decreased
  context: >-
    Inappropriately low urine osmolality in the face of a rising plasma
    osmolality is the physiological signature of the disease. Values below
    300 mOsm/kg after water deprivation, rising by more than 50 per cent on
    desmopressin, define complete arginine vasopressin deficiency; partial
    deficiency lands in an intermediate band that the water deprivation test
    handles poorly.
  biomarker_term:
    preferred_term: urine osmolality
    term:
      id: NCIT:C89824
      label: Osmolality
  readouts:
  - target: Impaired Renal Free Water Reabsorption
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Reports the collecting duct's failure to concentrate, which is the renal
      node itself rather than the hormone deficit upstream of it.
    evidence:
    - reference: PMID:38087160
      reference_title: New insights on diagnosis and treatment of AVP deficiency.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Patients were urinary osmolality stays below 300 mosm/kg but increases over 50% upon desmopressin administration are diagnosed as having complete AVP-D."
      explanation: >-
        Gives the diagnostic thresholds for this readout. The sentence is
        garbled in the source ("Patients were urinary osmolality stays") and is
        quoted verbatim as required.
  evidence:
  - reference: PMID:19897608
    reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
      infancy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "while urine osmolality remained between 73 and 229 mOsm/kg"
    explanation: Measured values in affected patients, showing how far below plasma the urine
      osmolality sits.
- name: Serum sodium
  presence: Increased
  context: >-
    Normal in a compensated patient with free access to water, so a normal
    sodium never excludes the diagnosis. It rises when compensation fails, and
    it is also the parameter that has to be watched in the opposite direction
    once desmopressin is started, because dilutional hyponatraemia is the main
    treatment complication.
  biomarker_term:
    preferred_term: sodium
    term:
      id: NCIT:C830
      label: Sodium
  readouts:
  - target: Hypernatremic Dehydration
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: MONITORING
    interpretation: Reports the decompensated state, and is monitored bidirectionally once
      desmopressin is in use.
    evidence:
    - reference: PMID:19897608
      reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
        infancy.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Patients developed hypernatremia (154-163 mmol/l) and serum hyperosmolality (>320 mOsm/kg)"
      explanation: Gives the measured sodium range in decompensated affected patients.
  evidence:
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The first days of treatment should be followed by monitoring of plasma sodium to avoid hyponatremia. Once a stable dose of desmopressin is established, annual monitoring of plasma sodium and kidney function should be performed."
    explanation: Establishes plasma sodium as the monitored analyte on treatment, which is
      the other half of why it is recorded here.
genetic:
- name: AVP
  gene_term:
    preferred_term: AVP
    term:
      id: hgnc:894
      label: AVP
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  association: Heterozygous mutation of the signal peptide or neurophysin II moiety,
    autosomal dominant; homozygous p.Pro26Leu, autosomal recessive
  frequency: The single causative gene for both the dominant and the recessive hereditary
    forms
  notes: >-
    The mutational spectrum is the mechanistic argument. Alleles cluster in the
    signal peptide and in neurophysin II - the parts of the precursor needed for
    signal cleavage, folding and dimerisation - and spare the mature nonapeptide
    in the dominant form. Nonsense, missense and initiation-codon alleles all
    produce the same phenotype, which is what a folding-and-retention mechanism
    predicts and a simple loss-of-hormone mechanism does not. Genotype does not
    predict age at onset or severity even within one small cohort, so molecular
    testing confirms the diagnosis but does not stratify it. The one allele that
    breaks the pattern is p.Pro26Leu, which sits in the mature hormone, is
    recessive, and works by a different mechanism entirely.
  evidence:
  - reference: PMID:33433888
    reference_title: 'Familial neurohypophyseal diabetes insipidus: clinical, genetic and functional
      studies of novel mutations in the arginine vasopressin gene.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These consisted of one initiation codon mutation in the signal peptide coding region (c.2T > C, p.Met1?), three missense mutations in the neurophysin II (NPII) coding region (c.154T > C, p.Cys52Arg; c.289C > G, p.Arg97Gly; and c.293G > C, p.Cys98Ser), and one nonsense mutation in the NPII coding region (c.343G > T, p.Glu115Ter)."
    explanation: Illustrates the allelic spectrum and its confinement to the signal peptide
      and neurophysin II across one cohort of five families.
  - reference: PMID:33433888
    reference_title: 'Familial neurohypophyseal diabetes insipidus: clinical, genetic and functional
      studies of novel mutations in the arginine vasopressin gene.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients showed progressive symptoms of polyuria and polydipsia, but with wide variability in severity and age at onset. No clear genotype-phenotype correlation was observed."
    explanation: The basis for the statement that genotype does not stratify the phenotype.
  - reference: PMID:31588537
    reference_title: Hereditary Neurohypophyseal Diabetes Insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Hereditary neurohypophyseal DI is caused by mutations in the gene encoding the antidiuretic hormone vasopressin (AVP) and its carrier protein neurophysin II (NPII)."
    explanation: Establishes AVP as the causative gene for the hereditary disease, covering
      both the hormone and the carrier-protein moieties of the same transcript.
inheritance:
- name: Autosomal dominant
  description: >-
    The usual mode. Fully penetrant heterozygous AVP mutations transmit through
    successive generations, and each child of an affected parent is at 50 per
    cent risk. Penetrance being complete does not mean expression is uniform:
    age at onset and severity vary widely between and within families, so an
    apparently mildly affected relative is still a carrier.
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:31785344
    reference_title: Role of protein aggregation and degradation in autosomal dominant neurohypophyseal
      diabetes insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The disease, manifesting in infancy or early childhood and gradually progressing in severity, is caused by fully penetrant heterozygous mutations in the gene encoding prepro-vasopressin-neurophysin II, the precursor of the antidiuretic hormone arginine vasopressin (AVP)."
    explanation: States full penetrance and heterozygosity, which together define the
      dominant mode here.
  - reference: PMID:31588537
    reference_title: Hereditary Neurohypophyseal Diabetes Insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Most commonly, the disease is transmitted in an autosomal dominant fashion; very rarely, autosomal recessive inheritance has been observed."
    explanation: Gives the relative frequency of the two modes, which is why the dominant
      form is treated as the default in this entry.
- name: Autosomal recessive
  description: >-
    Rare, and reported in consanguineous families. Homozygosity for AVP
    p.Pro26Leu causes disease while heterozygous parents are entirely
    asymptomatic - the clean genetic demonstration that this allele does not
    have the dominant alleles' toxic property. Deletion of the AVP locus is the
    other recorded recessive route.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:10369876
    reference_title: Autosomal recessive familial neurohypophyseal diabetes insipidus with continued
      secretion of mutant weakly active vasopressin.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We studied an unusual Palestinian family consisting of asymptomatic first cousin parents and three children affected with neurohypophyseal diabetes insipidus, suggesting autosomal recessive inheritance."
    explanation: The pedigree evidence for recessive transmission, including the unaffected
      heterozygous parents.
  - reference: PMID:27156762
    reference_title: Genetic forms of neurohypophyseal diabetes insipidus.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "In most affected families, the disease is transmitted in an autosomal dominant manner, whereas autosomal recessive forms are much less frequent."
    explanation: Places the recessive mode as much less frequent, which is how it is
      weighted in this entry.
progression:
- phase: Infancy
  notes: >-
    In the dominant form there is characteristically nothing at birth. This is
    the single most informative feature of the natural history and it is what
    rules out simple haploinsufficiency: a dosage problem would be present from
    the start, whereas a slowly accumulating aggregate needs time. In the
    recessive P26L form, by contrast, disease is manifest in the neonatal period
    with hypernatraemic dehydration - which the authors of that series read as
    direct evidence against the gradual-destruction mechanism operating there.
  evidence:
  - reference: PMID:19897608
    reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
      infancy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This is the first description of autosomal recessive FNDI presenting in the neonatal period. The unusual early clinical and radiological (MRI) presentation argues against gradual destruction of AVP-secreting neurons as the pathophysiological mechanism."
    explanation: >-
      Both halves of the claim in one sentence pair: the recessive form can
      present neonatally, and that timing is itself the argument that its
      mechanism is not progressive neuronal destruction.
- phase: Childhood
  notes: >-
    Polyuria and polydipsia appear, typically between one and six years of age,
    and deepen. Bedwetting and nocturia are often what brings the child to
    attention. The deficiency is frequently partial at this stage, so a water
    deprivation test can be equivocal in a child whose disease is unambiguous a
    few years later.
  evidence:
  - reference: PMID:19897608
    reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
      infancy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients typically present between 1 and 6 years of age with polyuria and polydipsia."
    explanation: Gives the age window for the typical dominant presentation.
  - reference: PMID:10443701
    reference_title: 'Clinical and molecular evidence of abnormal processing and trafficking of the
      vasopressin preprohormone in a large kindred with familial neurohypophyseal diabetes insipidus
      due to a signal peptide mutation.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The autosomal dominant form of familial neurohypophyseal diabetes insipidus (adFNDI) is a rare disease characterized by postnatal onset of polyuria and a deficient neurosecretion of the antidiuretic hormone, arginine vasopressin (AVP)."
    explanation: States the postnatal - not congenital - onset that defines this phase.
- phase: Adulthood
  notes: >-
    The hormone deficit is by now severe and does not remit; desmopressin
    dependence is lifelong. Post-mortem series in affected adults show frank
    degeneration of the vasopressinergic hypothalamic nuclei, so what began as
    reversible cellular dysfunction has become structural loss. The clinical
    burden shifts from the polyuria itself, which desmopressin controls, to the
    hazards of treatment and of interrupted access to it: dilutional
    hyponatraemia on one side, hypernatraemic dehydration during illness,
    fasting or hospitalisation on the other.
  evidence:
  - reference: PMID:31785344
    reference_title: Role of protein aggregation and degradation in autosomal dominant neurohypophyseal
      diabetes insipidus.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Post mortem studies in affected adults have shown cell degeneration in vasopressinergic hypothalamic nuclei."
    explanation: The structural endpoint that distinguishes this phase from the earlier
      functional one.
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Importantly, limited access to fluids or excessive fluid loss, for example, by non-availability or restricted intake, vomiting or diarrheal illnesses, unconsciousness, or acute concurrent illness, can lead to life-threatening dehydration"
    explanation: Names the circumstances that make this a dangerous condition in adult life
      despite effective replacement therapy.
diagnosis:
- name: Hypertonic saline-stimulated copeptin
  presence: PRESENT
  description: >-
    The current reference test. Plasma sodium is raised to at least 150 mmol/L
    with hypertonic saline and copeptin is measured at that point; a value at or
    below 4.9 pmol/L identifies vasopressin deficiency. It replaced the indirect
    water deprivation test on a head-to-head comparison in which it was
    substantially more accurate. It demands rapid bedside sodium measurement and
    close supervision, which is its practical cost.
  evidence:
  - reference: PMID:30067922
    reference_title: A Copeptin-Based Approach in the Diagnosis of Diabetes Insipidus.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Overall, among the 141 patients included in the analysis, the indirect water-deprivation test determined the correct diagnosis in 108 patients (diagnostic accuracy, 76.6%; 95% confidence interval [CI], 68.9 to 83.2), and the hypertonic saline infusion test (with a copeptin cutoff level of >4.9 pmol per liter) determined the correct diagnosis in 136 patients (96.5%; 95% CI, 92.1 to 98.6; P<0.001)."
    explanation: The head-to-head accuracy comparison and the copeptin threshold, in the
      trial that established both.
- name: Arginine-stimulated copeptin
  presence: PRESENT
  description: >-
    An alternative stimulation test proposed on grounds of simplicity: arginine
    is infused instead of hypertonic saline, so no bedside sodium monitoring and
    no induced hypernatraemia are needed. That practical advantage is the reason
    it was put forward, and it is what makes it usable where the reference test
    is not. The operating point is copeptin measured 60 minutes after the start
    of a body-weight-adapted infusion, with a cutoff of 3.8 pmol/L giving 93%
    diagnostic accuracy against primary polydipsia. Its main cost is nausea,
    which is not merely unpleasant: nausea and vomiting are themselves strong
    non-osmotic stimuli of AVP and copeptin release, so a symptomatic patient
    confounds the analyte the test measures, and a result obtained during severe
    nausea is interpretable only if copeptin stayed low. It is recorded here as
    an alternative rather than a replacement: sixty patients took part in both
    stimulation studies, and a post-hoc comparison within that overlap gave 100%
    diagnostic accuracy for hypertonic saline against 93% for arginine, which the
    review attributes to hypertonic saline being the stronger copeptin stimulus.
    What arginine buys in exchange is a simpler protocol and better tolerance.
  notes: >-
    The diagnostic-accuracy figures across this section come from different
    analyses, and only some of them can be lined up. Two are genuine within-cohort
    comparisons: the 141-patient trial supplies 96.5% for hypertonic saline
    against 76.6% for the water deprivation test, and the post-hoc analysis of
    the sixty patients who took part in both stimulation studies supplies 100%
    for hypertonic saline against 93% for arginine. What cannot be chained is
    one of those comparisons to the other: 100% and 96.5% are the same test
    measured in different patient sets, the sixty being those who also took
    part in the arginine study rather than an independent cohort. The 70-77%
    quoted on the water deprivation entry is a range across two prospective
    studies, one of them this same 141-patient trial, so the 76.6% sits inside
    that range rather than beside it.
  evidence:
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Due to its simplicity, arginine stimulated copeptin was put forward as alternative test procedure."
    explanation: >-
      States both the test and the reason it exists, in the review that surveys
      the copeptin-based options. Graded OTHER because "was put forward as" is
      the review's own editorial framing rather than a reported result.
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It was shown that copeptin measured 60 min after the start of the infusion using the cut-off level 3.8 pmol/L had the highest diagnostic accuracy of 93% to differentiate between patients with AVP-D and primary polydipsia [5]."
    explanation: >-
      Gives the test's operating point - timing, cutoff and accuracy - without
      which the entry describes a test a reader cannot apply. Graded
      HUMAN_CLINICAL rather than OTHER because the sentence reports the result
      of the prospective study in patients with polyuria-polydipsia syndrome,
      which is what evidence_source classifies; the OTHER items added alongside
      it quote the review's own framing, recommendation or synthesis instead.
      That distinction governs the items added here; it is not a claim about how
      every one of this reference's items in this file is graded, several of
      which are review narrative carrying HUMAN_CLINICAL from earlier curation.
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common adverse effect was mild nausea which occurred in 48% of the patients."
    explanation: >-
      Quantifies the test's principal adverse effect in the same study cohort.
      Nearly half is high enough that it belongs in the description rather than
      only in a tolerability footnote.
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "If severe nausea or vomiting occurs during arginine infusion, test results should therefore be interpreted cautiously and can only be used if copeptin concentrations remain low."
    explanation: >-
      The interpretive limit that follows from the adverse effect above, and the
      reason it matters mechanistically rather than only practically: nausea and
      vomiting stimulate AVP and copeptin directly, so they confound the analyte
      being measured. Graded OTHER because the sentence is the review's
      recommendation on how to read a result, not a reported measurement.
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "In summary, of the copeptin stimulation tests currently available, hypertonic saline stimulation ... provided the highest diagnostic accuracy, while arginine stimulation ... has a simpler test protocol and better test tolerance."
    explanation: >-
      Fixes the arginine test's position relative to the reference test in the
      review's own words, naming both in one sentence rather than leaving it to
      be inferred from a statement about hypertonic saline alone, and carrying
      the tolerability trade-off that is the reason the alternative exists. The
      ellipses stand for two inline numeric citation markers: the reference
      validator strips such markers from the snippet but not from the cached
      text and then matches the result whole, so a span crossing one fails,
      while an ellipsis bridge over each one verifies (dismech#10734). Graded
      OTHER because the sentence is the review's own cross-study synthesis
      rather than a result it reports - the same reason the "was put forward as"
      quote above is OTHER, and the distinction from the 48% nausea item, which
      reports the study's own number.
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sixty patients participated in both the hypertonic saline ... and the arginine ... stimulation study."
    explanation: >-
      Establishes the overlap the within-cohort comparison rests on. The
      head-to-head quote below says "these patients" without naming them, so
      without this the size and identity of that cohort were carried only by
      prose. Graded HUMAN_CLINICAL because the sentence reports the studies'
      composition rather than the review's framing of it. The ellipses bridge
      the two inline citation markers, per the convention noted at the synthesis
      item above.
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A post-hoc head-to-head comparison of these patients revealed a diagnostic accuracy of 100% for hypertonic stimulated copeptin compared to 93% for arginine stimulated copeptin."
    explanation: >-
      Ranks the two stimulation tests against each other in one cohort - the
      sixty patients who took part in both studies - so the entry can state the
      trade-off with a number instead of lining up figures from separate trials.
      Graded HUMAN_CLINICAL because the sentence reports the result of an
      analysis of patient data, even though that analysis is post-hoc.
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Likely, hypertonic saline infusion provides a stronger copeptin stimulus."
    explanation: >-
      The mechanism the review offers for the accuracy gap above, which is why
      the description attributes it rather than asserting it. Graded OTHER
      because "Likely" marks it as the authors' inference from the comparison
      rather than something the study measured. No directness value: the quote
      asserts the claim it is cited for, so the hedge is about the source's
      confidence, which that slot does not record.
- name: Indirect water deprivation test
  presence: PRESENT
  description: >-
    The historical gold standard, still widely performed. Urine concentrating
    ability is assessed over a fluid-restriction period and then challenged with
    desmopressin. Its weakness is precisely where this disease often sits early
    on - partial deficiency - and its published cutoffs were derived from a
    single small study that was never prospectively validated.
  evidence:
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In view of these limitations, it was not surprising that two prospective studies evaluating the diagnostic accuracy of the indirect water deprivation test found the diagnostic accuracy to be only 70–77%, with especially low accuracy in the difficult differentiation between partial AVP-D and PP patients"
    explanation: Quantifies the test's accuracy and locates its failure in the partial-deficiency
      differential that matters most in this disease.
- name: Absent posterior pituitary bright spot on T1 MRI
  presence: PRESENT
  description: >-
    The T1 hyperintensity of the normal posterior pituitary is attributed to
    vasopressin stored in neurosecretory granules, so its loss is the imaging
    correlate of the depleted and degenerating neurohypophyseal system and is
    the classic supporting observation in this disease. It is supporting rather
    than decisive: the bright spot is absent in only about 70 per cent of
    patients with vasopressin deficiency and in 39 per cent of patients with
    primary polydipsia, it disappears with age in healthy people, and it
    persists in some genuinely affected patients.
  evidence:
  - reference: PMID:19897608
    reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
      infancy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Plasma AVP levels were low, and the posterior pituitary bright spot was absent on magnetic resonance imaging (MRI)."
    explanation: Records the finding in molecularly confirmed hereditary disease, alongside
      the low hormone level it is taken to reflect.
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "its absence was shown in 70% of patients with AVP-D but also 39% of patients with primary polydipsia"
    explanation: >-
      The numbers that make this a supporting rather than a pathognomonic sign,
      and the reason the entry does not model it as a phenotype.
- name: AVP molecular genetic testing
  presence: PRESENT
  description: >-
    Sequencing AVP confirms the diagnosis, distinguishes the dominant from the
    recessive form, and is what makes presymptomatic testing of at-risk
    relatives possible - which matters because in the dominant form the
    biochemical abnormality lags the genotype by years. It does not predict when
    the disease will start or how severe it will be.
  evidence:
  - reference: PMID:33433888
    reference_title: 'Familial neurohypophyseal diabetes insipidus: clinical, genetic and functional
      studies of novel mutations in the arginine vasopressin gene.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Five Portuguese families with autosomal dominant FNDI underwent sequencing of the AVP gene and the identified mutations were functionally characterized by in vitro studies."
    explanation: >-
      Documents AVP sequencing as the diagnostic route in familial disease. The
      quote establishes the practice rather than asserting a diagnostic yield,
      hence directness INDIRECT.
    directness: INDIRECT
treatments:
- name: Desmopressin
  description: >-
    The standard of care and, in practice, the whole of treatment. Desmopressin
    is a synthetic vasopressin analogue differing by two amino acids, which
    lengthen its half-life and remove the vasopressor activity, leaving a
    selective V2 agonist. Oral, intranasal and parenteral formulations exist;
    oral is now preferred on tolerability and safety grounds. It replaces the
    missing hormone and does nothing whatever to the aggregating precursor
    upstream, so the neuronal disease continues underneath a controlled
    phenotype - which is why disease-modifying approaches are of interest even
    though symptom control is good. Dosing is individualised and starts at
    bedtime to control nocturia.
  action_category: THERAPEUTIC
  therapeutic_modality: PEPTIDE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: desmopressin
      term:
        id: CHEBI:4450
        label: desmopressin
  target_mechanisms:
  - target: Impaired Renal Free Water Reabsorption
    treatment_effect: BYPASSES
    description: >-
      Supplying an exogenous V2 agonist restores aquaporin-mediated water
      reabsorption at the collecting duct without restoring endogenous hormone
      production, so it bypasses every upstream node rather than correcting any
      of them.
    evidence:
    - reference: PMID:38087160
      reference_title: New insights on diagnosis and treatment of AVP deficiency.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Desmopressin differs from AVP by two amino acids and is available in parenteral, oral and nasal formulations, providing effective long-term control of polyuria."
      explanation: Identifies the agent as a hormone analogue acting at the renal receptor and
        records that it controls the renal phenotype long term.
  evidence:
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Desmopressin, a synthetic AVP analogue and selective V2 receptor agonist, is the current standard of care and is usually initiated after the diagnosis of AVP-D is confirmed"
    explanation: Establishes desmopressin as the standard of care and names its
      pharmacological class.
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Desmopressin treatment provides immediate symptomatic relief; however, the main complication is dilutional hyponatremia and its associated risk of cerebral edema, seizure, coma and even death"
    explanation: >-
      The principal hazard of the treatment. It is recorded on the treatment
      itself rather than as a phenotype because it is iatrogenic, not a feature
      of the disease.
  - reference: PMID:19897608
    reference_title: 'Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early
      infancy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients responded to desmopressin."
    explanation: >-
      Confirms responsiveness in the recessive subtype specifically, which is
      not obvious a priori: the endogenous hormone there is present but weak, so
      the drug works by supplying a full agonist rather than by filling a void.
  notes: >-
    Hyponatraemia is common enough on treatment - reported at up to 30 per cent
    in outpatients - that deliberate periodic omission of a dose to allow
    aquaresis, so-called desmopressin escape, is recommended, and patients need
    explicit education on the symptoms.
- name: Assured Access to Water and Fluid Management
  description: >-
    Not an afterthought. Because osmoregulated thirst is intact in almost all
    patients, free access to water is what actually maintains water balance, and
    the situations that remove it - fasting for surgery, vomiting or diarrhoeal
    illness, unconsciousness, an inpatient team unfamiliar with the condition -
    are the ones that kill. The management of dehydration when it occurs is
    replacement of roughly half the calculated free water deficit over the first
    24 hours with hypotonic fluid.
  action_category: THERAPEUTIC
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_mechanisms:
  - target: Hypernatremic Dehydration
    treatment_effect: INHIBITS
    description: >-
      Maintaining intake against an obligate renal water loss prevents the
      hypertonic decompensation, which is the only life-threatening event in the
      natural history of a treated patient.
    evidence:
    - reference: PMID:38087160
      reference_title: New insights on diagnosis and treatment of AVP deficiency.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Therefore, hypernatremia, an indicator of inadequate fluid balance, rarely occurs in AVP-D patients with free access to fluids"
      explanation: States the protective effect directly - free access to fluids is what keeps
        hypernatraemia rare.
  evidence:
  - reference: PMID:38087160
    reference_title: New insights on diagnosis and treatment of AVP deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The main treatment goals in patients with AVP-D are the correction of pre-existing water deficits and the reduction of excessive urinary water loss."
    explanation: States the two treatment goals, of which this intervention addresses the
      first and desmopressin the second.
animal_models:
- name: FNDI knock-in mouse (mutant neurophysin II)
  species: Mouse
  genotype: Heterozygous Avp knock-in encoding a mutant neurophysin II
  publication: PMID:19297548
  description: >-
    The workhorse model of this disease and the source of nearly everything
    known about the timing of the mechanism. Heterozygous mice develop
    progressive polyuria as patients do, and the model has been used to separate
    the two arms of the cascade in time: aggregates accumulate and AVP
    transcription falls first, and neuronal death follows only later and only
    under osmotic load. Because the phenotype can be accelerated by intermittent
    water deprivation, the model also permits the neuron-loss endpoint to be
    reached in weeks rather than in the animal's whole lifespan.
  genes:
  - preferred_term: AVP
    term:
      id: hgnc:894
      label: AVP
  evidence:
  - reference: PMID:19297548
    reference_title: Progressive polyuria without vasopressin neuron loss in a mouse model for familial
      neurohypophysial diabetes insipidus.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Here we analyzed knockin mice expressing mutant NPII that causes FNDI in humans. The heterozygous mice manifested progressive polyuria as do patients with FNDI."
    explanation: Establishes the model, the human allele class it carries, and the cardinal
      phenotype it reproduces.
  modeled_mechanisms:
  - target: Endoplasmic Reticulum Retention and Fibrillar Aggregation
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: MOLECULAR
    description: >-
      Aggregates form in the endoplasmic reticulum of supraoptic AVP neurons and
      grow in step with urine volume, so the model reproduces the retained
      aggregate in the correct cell type and in the correct temporal relation to
      the phenotype.
    limitations: >-
      The aggregates are not stained by antibodies to mutant neurophysin II,
      normal neurophysin II or AVP, so their exact composition in vivo is not
      established by the immunohistochemistry alone.
    readouts:
    - name: Inclusion body size in supraoptic nucleus AVP cells
      target: Endoplasmic Reticulum Retention and Fibrillar Aggregation
      direction: INCREASED
      interpretation: Morphological measure of the accumulating aggregate, tracked against
        urine volume in the same animals.
      evidence:
      - reference: PMID:19297548
        reference_title: Progressive polyuria without vasopressin neuron loss in a mouse model for familial
          neurohypophysial diabetes insipidus.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "the size of inclusion bodies gradually increased in parallel with the increases in urine volume"
        explanation: Reports the measurement and its direction, and ties it quantitatively to
          the phenotype.
    evidence:
    - reference: PMID:19297548
      reference_title: Progressive polyuria without vasopressin neuron loss in a mouse model for familial
        neurohypophysial diabetes insipidus.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "At 12 mo, dilated ER filled with aggregates occupied the cytoplasm of AVP cells, while few aggregates were found in the nucleus."
      explanation: Ultrastructural confirmation that the aggregate is where the mechanism says
        it should be, in a dilated ER of the affected neuron.
  - target: Vasopressin Neuron Secretory Dysfunction
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: CELLULAR
    description: >-
      AVP mRNA in the supraoptic nucleus falls while the AVP-expressing cell
      count is unchanged, which is the direct in-vivo demonstration that
      secretory failure precedes cell loss.
    readouts:
    - name: AVP mRNA expression in supraoptic nucleus
      target: Vasopressin Neuron Secretory Dysfunction
      direction: DECREASED
      interpretation: In situ hybridisation measure of hormone-gene expression in the
        surviving neurons.
      evidence:
      - reference: PMID:19297548
        reference_title: Progressive polyuria without vasopressin neuron loss in a mouse model for familial
          neurohypophysial diabetes insipidus.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Analyses with in situ hybridization revealed that expression of AVP mRNA was significantly decreased in the SON in the heterozygous mice compared with that in wild-type mice."
        explanation: The measurement and its direction.
  - target: Magnocellular Vasopressin Neuron Loss
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: >-
      Neuronal loss does occur, but only when the mutant neurons are driven by
      sustained osmotic demand; 30 to 40 per cent of AVP neurons are lost after
      twelve weeks of water deprivation.
    limitations: >-
      In unstressed animals the polyuria progresses substantially with no
      neuronal loss at all, so the timing of loss in this model is set by an
      experimental manipulation and cannot be read straight across to the human
      natural history. What the model shows is that loss is possible and
      demand-dependent, not when it happens in a patient.
    readouts:
    - name: Surviving AVP neuron count after intermittent water deprivation
      target: Magnocellular Vasopressin Neuron Loss
      direction: DECREASED
      interpretation: Cell counts after a defined osmotic challenge, the endpoint that
        establishes the degenerative arm of the mechanism.
      evidence:
      - reference: PMID:29961215
        reference_title: A novel mechanism of autophagy-associated cell death of vasopressin neurons in
          familial neurohypophysial diabetes insipidus.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "at which stage 30-40% of AVP neurons were lost"
        explanation: The quantitative loss measured at the twelve-week water-deprivation
          endpoint.
    evidence:
    - reference: PMID:19297548
      reference_title: Progressive polyuria without vasopressin neuron loss in a mouse model for familial
        neurohypophysial diabetes insipidus.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Counting cells expressing AVP mRNA in the SON indicated that polyuria had progressed substantially in the absence of neuronal loss."
      explanation: >-
        The negative half of the same claim, and the reason this link is
        PARTIALLY_RECAPITULATES rather than RECAPITULATES: without an osmotic
        challenge the model's polyuria is not accompanied by cell loss.
  - target: Endoplasmic Reticulum Retention and Fibrillar Aggregation
    relationship: RESCUES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: >-
      The chemical chaperone 4-phenylbutyrate reduced mutant protein
      accumulation in the ER of these mice, increased AVP release, cut urine
      volume and attenuated neuron loss under salt loading. This is the
      pharmacological test of the mechanism: relieving the ER burden improves
      both the hormone deficit and the degeneration, which is what a
      proteotoxicity model predicts and a haploinsufficiency model does not.
    limitations: >-
      A preclinical result in mice with no human trial in this disease; the entry
      records no corresponding treatment. It also does not establish which of the
      several downstream consequences of ER burden the benefit runs through.
    readouts:
    - name: Urine volume on 4-phenylbutyrate
      target: Endoplasmic Reticulum Retention and Fibrillar Aggregation
      direction: RESTORED
      interpretation: The organism-level output used to judge the rescue, alongside the
        molecular readout of reduced ER accumulation.
      evidence:
      - reference: PMID:29886132
        reference_title: Chemical chaperone 4-phenylbutylate reduces mutant protein accumulation in the
          endoplasmic reticulum of arginine vasopressin neurons in a mouse model for familial neurohypophysial
          diabetes insipidus.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Treatment with 4-PBA reduced mutant protein accumulation in the ER of FNDI mice and increased AVP release, leading to reduced urine volumes."
        explanation: Reports the intervention and the direction of both the molecular and the
          physiological readout.
    evidence:
    - reference: PMID:29886132
      reference_title: Chemical chaperone 4-phenylbutylate reduces mutant protein accumulation in the
        endoplasmic reticulum of arginine vasopressin neurons in a mouse model for familial neurohypophysial
        diabetes insipidus.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Furthermore, AVP neuron loss under salt loading was attenuated by 4-PBA treatment."
      explanation: Shows the rescue reaches the degenerative endpoint and not only the
        molecular one, which is what makes the ER burden causal rather than incidental.
- name: Cys67stop FNDI transgenic rat
  species: Rat
  genotype: Cys67stop mutant vasopressin transgene expressed in magnocellular neurons
  publication: PMID:12153465
  description: >-
    An earlier transgenic rat expressing a truncating FNDI allele in vasopressin
    magnocellular neurons. Its contribution is the autophagy arm: it showed that
    the mutant protein accumulates in a swollen, distended ER that also holds
    wild-type endogenous vasopressin, and that the resulting vesicles are
    degradative autolysosomes rather than secretory structures.
  genes:
  - preferred_term: AVP
    term:
      id: hgnc:894
      label: AVP
  evidence:
  - reference: PMID:12153465
    reference_title: Autophagy in hypothalamic neurones of rats expressing a familial neurohypophysial
      diabetes insipidus transgene.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In rats expressing an FNDI mutant transgene (Cys67stop) in vasopressin magnocellular neurones, the mutant protein fails to enter the regulated secretory pathway, and accumulates in a swollen and distended endoplasmic reticulum (ER) that also contains wild-type, endogenous vasopressin."
    explanation: >-
      Establishes the model and, in the same sentence, the co-retention of
      wild-type hormone that underlies the dominance of the human disease.
  modeled_mechanisms:
  - target: Endoplasmic Reticulum Stress and Autophagy Induction
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Lysosomal and late-endosomal markers are upregulated specifically in the
      cells expressing the mutant transgene, and the aggregate-containing
      vesicles are immunoreactive for cathepsin D, endolyn and LAMP1.
    limitations: >-
      A transgene overexpressing a truncated allele rather than a knock-in of a
      patient mutation at the endogenous locus, so expression level and the
      species of retained protein both differ from the human situation. The
      readouts are marker immunoreactivity rather than flux measurements, so
      autophagic activity is inferred from the presence of autolysosomes.
    evidence:
    - reference: PMID:12153465
      reference_title: Autophagy in hypothalamic neurones of rats expressing a familial neurohypophysial
        diabetes insipidus transgene.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "We have now examined the expression of vesicular markers in our transgenic rats, and demonstrate that activation of autolysosomal processes is a consequence of the expression of Cys67stop."
      explanation: >-
        Attests that this model is informative for the autophagy node
        specifically, and states the causal direction the authors claim -
        autolysosomal activation is a consequence of expressing the mutant.
    readouts:
    - name: Lysosomal marker expression in transgene-expressing neurons
      target: Endoplasmic Reticulum Stress and Autophagy Induction
      direction: INCREASED
      interpretation: Cell-type-restricted upregulation of lysosomal markers, the evidence that
        autophagy is engaged by the mutant protein specifically.
      evidence:
      - reference: PMID:12153465
        reference_title: Autophagy in hypothalamic neurones of rats expressing a familial neurohypophysial
          diabetes insipidus transgene.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "In addition, there is an up-regulation of lysosomal markers specifically in cells expressing Cys67stop."
        explanation: The measurement, its direction and its restriction to the affected cells.
- name: Sel1L-Hrd1 ERAD-deficient mouse
  species: Mouse
  genotype: Global or AVP-neuron-specific ablation of Sel1L-Hrd1 ER-associated degradation
  publication: PMID:28920920
  description: >-
    Not a model of the mutation, but a model of the mechanism's capacity limit,
    and for that reason one of the most informative animals in this literature.
    Removing the Sel1L-Hrd1 ERAD complex from vasopressin neurons that carry two
    normal AVP alleles is sufficient to produce ER retention, disulfide-bonded
    aggregation of proAVP and progressive diabetes insipidus. It shows that the
    disease phenotype follows from ERAD being overwhelmed, whichever side of the
    balance moves - a mutant client the machinery cannot handle, or intact
    clients with no machinery.
  evidence:
  - reference: PMID:28920920
    reference_title: ER-associated degradation is required for vasopressin prohormone processing and
      systemic water homeostasis.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Mice with global or AVP neuron-specific ablation of Se1L-Hrd1 ERAD progressively developed polyuria and polydipsia, characteristics of diabetes insipidus."
    explanation: >-
      Establishes the model and the phenotype it produces. The abstract prints
      the gene as "Se1L" for Sel1L; the snippet reproduces the source exactly.
  modeled_mechanisms:
  - target: Endoplasmic Reticulum Retention and Fibrillar Aggregation
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      Reproduces the ER retention and intermolecular disulfide-bonded
      aggregation of proAVP that the human dominant alleles produce, and
      identifies protein disulfide isomerase activity as what drives the
      inappropriate cross-linking.
    limitations: >-
      The genetic lesion is in the quality-control machinery, not in AVP, so the
      model speaks to why retention is pathogenic and not to why a particular
      patient allele is retained. Loss of Sel1L-Hrd1 also removes ERAD for every
      other client in the neuron, so some of the phenotype may not run through
      proAVP at all.
    readouts:
    - name: Disulfide-bonded proAVP aggregate formation
      target: Endoplasmic Reticulum Retention and Fibrillar Aggregation
      direction: INCREASED
      interpretation: Biochemical measure of the aggregate species, in animals whose proAVP
        sequence is entirely normal.
      evidence:
      - reference: PMID:28920920
        reference_title: ER-associated degradation is required for vasopressin prohormone processing
          and systemic water homeostasis.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "The inability to clear misfolded proAVP with highly reactive cysteine thiols in the absence of Sel1L-Hrd1 ERAD causes proAVP to accumulate and participate in inappropriate intermolecular disulfide-bonded aggregates, promoted by the enzymatic activity of protein disulfide isomerase (PDI)."
        explanation: Reports the aggregate species and the chemistry that forms it, which is
          the same disulfide-linked fibrillar aggregate described in patients' alleles.
    evidence:
    - reference: PMID:28920920
      reference_title: ER-associated degradation is required for vasopressin prohormone processing and
        systemic water homeostasis.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Further, we show that proAVP is an endogenous substrate of Sel1L-Hrd1 ERAD."
      explanation: >-
        Establishes that this model acts on the node's own substrate rather than
        on the neuron generically, which is what makes the link informative.
- name: Brattleboro rat
  species: Rat
  genotype: Homozygous Avp single-guanine deletion in the neurophysin coding region (frameshift)
  publication: PMID:9756087
  description: >-
    The classical rodent model of central diabetes insipidus and the animal
    almost every physiological study of vasopressin replacement has used. It is
    recorded here for what it does not model. The lesion is a recessive
    frameshift that removes the normal stop codon and extends the C-terminus;
    the precursor is trapped in the ER, but the magnocellular neurons are
    preserved and there is no neurotoxicity, and the animals are affected only
    when homozygous. Every one of those is the opposite of the human dominant
    disease, so results obtained in this rat should not be read across to it.
  evidence:
  - reference: PMID:9756087
    reference_title: 'Vasopressin processing defects in the Brattleboro rat: implications for hereditary
      central diabetes insipidus in humans?'
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The mutated AVP gene precursor of Brattleboro rat has a deletion of a single base, guanine, in the neurophysin coding region that leads to a frameshift resulting in the loss of the normal stop codon."
    explanation: Establishes the model and its causal allele, which is the basis for the
      comparison drawn below.
  modeled_mechanisms:
  - target: Magnocellular Vasopressin Neuron Loss
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    model_scale: CELLULAR
    description: >-
      The Brattleboro rat retains its magnocellular vasopressin neurons. It has
      the hormone deficiency without the neurodegeneration, so it cannot be used
      to study the proteotoxic arm of the human disease and cannot be used to
      argue that the arm is unnecessary.
    limitations: >-
      Recessive rather than dominant, a frameshift with a read-through
      C-terminus rather than a missense or nonsense allele, and neurons
      preserved rather than lost. The source itself concludes that findings in
      this animal are only partially applicable to human hereditary disease.
    evidence:
    - reference: PMID:9756087
      reference_title: 'Vasopressin processing defects in the Brattleboro rat: implications for hereditary
        central diabetes insipidus in humans?'
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "However, in contrast to the recessive defect in the Brattleboro rat, in human CDI, neurotoxicity and denigration of the magnocellular neurons have been observed, and dominant inheritance occurs."
      explanation: >-
        States the failure directly: neurotoxicity and magnocellular
        degeneration are human findings that this recessive rat does not show.
    - reference: PMID:9756087
      reference_title: 'Vasopressin processing defects in the Brattleboro rat: implications for hereditary
        central diabetes insipidus in humans?'
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Thus, the results from studies in the Brattleboro rat may only be partially applicable to hereditary CDI in humans."
      explanation: The authors' own limitation on transfer, which is the reason this model is
        recorded as a negative rather than omitted.
references:
- reference: PMID:9756087
  title: "Vasopressin processing defects in the Brattleboro rat: implications for hereditary central diabetes insipidus in humans?"
- reference: PMID:10085151
  title: "Mutant vasopressin precursors that cause autosomal dominant neurohypophyseal diabetes insipidus retain dimerization and impair the secretion of wild-type proteins."
- reference: PMID:10369876
  title: "Autosomal recessive familial neurohypophyseal diabetes insipidus with continued secretion of mutant weakly active vasopressin."
- reference: PMID:10443701
  title: "Clinical and molecular evidence of abnormal processing and trafficking of the vasopressin preprohormone in a large kindred with familial neurohypophyseal diabetes insipidus due to a signal peptide mutation."
- reference: PMID:12153465
  title: "Autophagy in hypothalamic neurones of rats expressing a familial neurohypophysial diabetes insipidus transgene."
- reference: PMID:15356057
  title: "Differential cellular handling of defective arginine vasopressin (AVP) prohormones in cells expressing mutations of the AVP gene associated with autosomal dominant and recessive familial neurohypophyseal diabetes insipidus."
- reference: PMID:19297548
  title: "Progressive polyuria without vasopressin neuron loss in a mouse model for familial neurohypophysial diabetes insipidus."
- reference: PMID:19897608
  title: "Autosomal recessive familial neurohypophyseal diabetes insipidus: onset in early infancy."
- reference: PMID:24121282
  title: "Endoplasmic reticulum stress in vasopressin neurons of familial diabetes insipidus model mice: aggregate formation and mRNA poly(A) tail shortening."
- reference: PMID:27156762
  title: "Genetic forms of neurohypophyseal diabetes insipidus."
- reference: PMID:28920920
  title: "ER-associated degradation is required for vasopressin prohormone processing and systemic water homeostasis."
- reference: PMID:29421628
  title: "[Nephrogenic diabetes insipidus]."
- reference: PMID:29886132
  title: "Chemical chaperone 4-phenylbutylate reduces mutant protein accumulation in the endoplasmic reticulum of arginine vasopressin neurons in a mouse model for familial neurohypophysial diabetes insipidus."
- reference: PMID:29961215
  title: "A novel mechanism of autophagy-associated cell death of vasopressin neurons in familial neurohypophysial diabetes insipidus."
- reference: PMID:30067922
  title: "A Copeptin-Based Approach in the Diagnosis of Diabetes Insipidus."
- reference: PMID:31588537
  title: "Hereditary Neurohypophyseal Diabetes Insipidus."
- reference: PMID:31785344
  title: "Role of protein aggregation and degradation in autosomal dominant neurohypophyseal diabetes insipidus."
- reference: PMID:33433888
  title: "Familial neurohypophyseal diabetes insipidus: clinical, genetic and functional studies of novel mutations in the arginine vasopressin gene."
- reference: PMID:34232487
  title: "Functional analyses of three different mutations in the AVP-NPII gene causing familial neurohypophyseal diabetes insipidus."
- reference: PMID:38087160
  title: "New insights on diagnosis and treatment of AVP deficiency."
- reference: PMID:41045372
  title: "Phagophores originate from endoplasmic reticulum membranes in vasopressin neurons in a mouse model of familial neurohypophysial diabetes insipidus."
notes: >-
  Scope. This entry is the hereditary neurohypophyseal entity, MONDO:0007450,
  and nothing else. Central diabetes insipidus is overwhelmingly acquired -
  surgical, traumatic, infiltrative, autoimmune, neoplastic - and nephrogenic
  diabetes insipidus is a different disease of the kidney, caused by AVPR2 or
  AQP2 defects. Neither is curated here. PMID:29421628 is a nephrogenic
  diabetes insipidus review and is cited only for the normal
  vasopressin-to-aquaporin-2 physiology of the collecting duct, with
  directness INDIRECT on both of its evidence items to record that. This is the
  first diabetes insipidus entry of any kind in the knowledge base, so the scope
  boundary is stated explicitly rather than left to be inferred from sibling
  entries.

  Naming. The field has largely renamed this condition arginine vasopressin
  deficiency (AVP-D), on patient-safety grounds: confusion with diabetes
  mellitus has caused deaths. The MONDO label is retained as disease_term
  because that is the schema contract, with AVP-D recorded as a synonym, and
  recent sources cited here use the new name throughout.

  The mechanism model, and why it has two arms. The entry deliberately splits
  the consequence of ER aggregation into "Vasopressin Neuron Secretory
  Dysfunction" and "Magnocellular Vasopressin Neuron Loss" rather than modelling
  a single neurodegeneration node, because the two are separable in time and the
  literature is explicit about it. PMID:19297548 counted AVP-mRNA-expressing
  cells in the knock-in mouse and found polyuria advancing substantially with no
  neuronal loss, concluding that cell death is not the primary cause of the
  polyuria. PMID:31785344 makes the same point for the transgenic models.
  Collapsing the two would assert, wrongly, that the polyuria is a consequence
  of cell death. Both arms converge on Progressive Arginine Vasopressin
  Deficiency, which is where the disease becomes systemic. The secretory-failure
  arm is reached by two routes that are modelled as separate edges: direct
  interference with the regulated secretory pathway by the retained aggregate,
  and an ER-stress-driven shortening of the AVP mRNA poly(A) tail that lowers
  transcript expression (PMID:24121282) - a throttling of supply that the cell
  performs on itself to reduce its unfolded-protein load.

  Gain of function, and which slot carries it. The variant consequence is
  recorded on the pathophysiology node's genetic_context as
  functional_impact_category: DOMINANT_NEGATIVE, not as
  modifier: GAIN_OF_FUNCTION on a process descriptor. Both terms are defensible
  descriptions of a toxic dominant allele, and the schema's decision table
  settles which slot they belong in: functional_impact_category is for the
  consequence of a variant, and this is a variant consequence. DOMINANT_NEGATIVE
  was chosen over NEOMORPHIC because it is what the primary literature
  demonstrates - PMID:10085151 showed mutant precursors heterodimerise with
  wild-type and block its ER-to-Golgi transit, and PMID:31785344 records
  wild-type precursor trapped inside the fibrillar aggregates. The toxic-gain
  framing, which is the broader and equally true statement, is carried in the
  node descriptions rather than forced into a single-valued enum.

  Module conformance. Two nodes conform to loss_of_proteostasis. The
  ER-aggregation node maps to "Misfolded-Protein Aggregation" and the
  neuron-loss node to "Proteotoxic Cell Dysfunction and Neurodegeneration". That
  module is tagged AGING, and this is a paediatric Mendelian disease, but
  conformance is per-node and the module's own description invites disorder
  entries to substitute their disease-specific aggregating protein; nine other
  Mendelian entries already conform to it. The module's upstream node,
  "Proteostasis Network Decline", is deliberately not conformed to, because
  nothing here suggests a general age-related decline of the proteostasis
  network - the network is normal and the client protein is not. The
  amyloidogenesis module was considered and rejected: it scopes itself to
  extracellular deposits, and these aggregates are inside the ER lumen.
  er_protein_storage_disease was also considered and rejected: it is explicitly
  a hepatocellular module ending in stellate-cell fibrosis, and although the
  first two steps of its chain are the same idea, conforming a hypothalamic
  neuron to a node named "Hepatic Protein Aggregation" would be wrong.

  The recessive subtype is modelled as a contrast, not as a milder variant. AR
  P26L has its own pathophysiology node, "Secreted Weakly Active Vasopressin",
  which enters the graph at the renal step and bypasses every ER node. This is
  the honest reading of PMID:15356057, which ran the dominant Y21H and the
  recessive P26L prohormones side by side in one experiment and found the first
  in the endoplasmic reticulum and the second in secretory granules; and of
  PMID:10369876, which measured serum Leu-AVP thirty times above normal in
  affected children. The clinical corollary is recorded in progression: the
  recessive form presents neonatally, and PMID:19897608 reads that timing as an
  argument against gradual neuronal destruction in that form.

  Negative and qualified models are recorded on purpose. The knock-in mouse only
  PARTIALLY recapitulates neuron loss, because without an osmotic challenge its
  polyuria progresses with no cell loss at all, and the Brattleboro rat carries
  a FAILS_TO_RECAPITULATE link against the neuron-loss node, because it is a
  recessive frameshift with preserved magnocellular neurons and no
  neurotoxicity. The Brattleboro rat is the workhorse of vasopressin physiology
  and it would be easy to list it here as the animal model of this disease; it
  is not one, and its own authors say results from it are only partially
  applicable. The Sel1L-Hrd1 ERAD-deficient mouse is included for the opposite
  reason: it carries no AVP mutation at all, and the fact that it still
  develops the disease is the cleanest evidence that ERAD capacity is what the
  mechanism turns on.

  Deep research. Two providers ran. Asta returned in five seconds
  (research/Neurohypophyseal_Diabetes_Insipidus-deep-research-asta.md; 37/37
  references resolved, none unresolved, no ontology CURIEs proposed) but its
  retrieval was poor for this disease - of twenty papers returned, most were
  about diabetes mellitus and its complications, and only three were about the
  right disease. Falcon returned after twelve minutes
  (research/Neurohypophyseal_Diabetes_Insipidus-deep-research-falcon.md; 18/20
  references resolved, 2 unverifiable, 1 flagged possibly off topic, and
  needs_review true because it labelled MONDO:0007450 "if available", which is
  template boilerplate echoed back rather than a term error). Falcon's report is
  scoped more broadly than this entry - it covers acquired central diabetes
  insipidus as well - and it cites by author-year key with no PMIDs, so nothing
  was quoted from it directly. Its ordered causal chain independently matches
  the model built here, including the caution that neuronal death is not
  required for early disease, and it supplied three leads that were then located
  in PubMed and cited: the Sel1L-Hrd1 ERAD mouse (PMID:28920920), the
  poly(A)-tail-shortening mechanism (PMID:24121282), and the Brattleboro rat as
  a model to be careful with (PMID:9756087). Everything else came from a
  systematic PubMed sweep. Falcon's prevalence figure of 1 in 25,000 was not
  used: it is keyed to unresolvable author-year citations, and it is a figure
  for arginine vasopressin deficiency overall, which is overwhelmingly acquired,
  not for the hereditary entity this entry covers.

  No GeneReviews chapter exists. PubMed was searched three ways - the disease
  name with GeneReviews, the GeneReviews[Book] publication type crossed with
  vasopressin, neurohypophyseal and central diabetes insipidus, and AVP in the
  title with GeneReviews - and the only diabetes insipidus chapter in
  GeneReviews is Hereditary Nephrogenic Diabetes Insipidus (PMID:20301356),
  which is a different disease and is not cited here. WFS1 Spectrum Disorder
  (PMID:20301750) also surfaced and is likewise a different entity, although
  Wolfram syndrome is the differential worth remembering in a child with central
  diabetes insipidus. The mandatory GeneReviews phenotype baseline could
  therefore not be applied; the phenotype set is drawn from the primary clinical
  literature instead.

  Quoting notes. Four cached sources contain errors that are reproduced verbatim
  in snippets, as the evidence rules require, and each is flagged in its own
  explanation: PMID:10443701 prints the allele as "Ala(- 1)Thr" with a stray
  space; PMID:38087160 gives the copeptin cut-off unit as mmol/L where the
  primary trial (PMID:30067922) reports pmol per litre, and also contains a
  garbled sentence beginning "Patients were urinary osmolality stays"; and
  PMID:28920920 prints the gene as "Se1L" for Sel1L. None of these were
  corrected in the quotes.

  Two phenotypes are deliberately left unconnected in the causal graph. Failure
  to Thrive in Infancy and Vomiting are reported by PMID:19897608 as the
  presenting features of the recessive infants, with hypernatraemia and
  hyperosmolality recorded as something the patients subsequently "developed".
  Wiring them as sequelae of Hypernatremic Dehydration would therefore invert
  the order the source reports, and no source was found that establishes the
  direction, so they are left as unconnected phenotype nodes. Two renal edges
  that are physiologically certain - impaired free water reabsorption to
  hyposthenuria and to nocturia - are drawn but carry no separate edge
  citation, since the only quotes available support the nodes rather than the
  step between them.

  Known extension points. Clinical trials, for which no trial specific to the
  hereditary form was identified. Datasets, none found for this disease.
  Computational models. A comorbidity or grouping link to the other ER storage
  diseases, which would be a better home for the cross-disease comparison than
  this entry's notes. Oxytocin deficiency, which recent work raises as a
  possible contributor to the psychological morbidity reported in this
  population, and which would need its own evidence rather than the general
  statements available now. And 4-phenylbutyrate, which is recorded here only as
  a rescue arm on the mouse model - if it ever reaches a human trial it becomes
  a treatment entry with a disease-modifying target_mechanisms link to the
  aggregation node rather than the bypass link desmopressin has.

📚

References & Deep Research

References

PMID:9756087

Vasopressin processing defects in the Brattleboro rat: implications for hereditary central diabetes insipidus in humans?