Familial Glucocorticoid Deficiency

Mendelian MONDO:0008733 Pathograph 20 Show in embeddings browser Adrenal Insufficiency Chronic Primary Adrenal Insufficiency

Familial glucocorticoid deficiency (FGD) is a genetically heterogeneous group of autosomal recessive primary adrenal insufficiency disorders characterized by isolated failure of cortisol production in response to adrenocorticotropic hormone (ACTH), with classically preserved mineralocorticoid (aldosterone) secretion, because the aldosterone-producing zona glomerulosa is regulated principally by the renin-angiotensin system rather than by ACTH. Affected infants and children present with hypoglycemia, generalized hyperpigmentation (driven by markedly elevated ACTH and other POMC-derived peptides), failure to thrive, and recurrent or severe infections; unlike combined glucocorticoid-and-mineralocorticoid primary adrenal insufficiency, salt-wasting, hyponatremia, and hyperkalemia are characteristically absent. Two mechanistically distinct routes converge on the same endocrine endpoint: failure of ACTH receptor signaling itself (MC2R, the ACTH receptor, and its obligate trafficking chaperone MRAP, together accounting for roughly 45% of cases, plus partial-function mutations in STAR, the rate-limiting cholesterol-transport step of steroidogenesis) versus adrenocortical cell loss from failure of mitochondrial antioxidant defense (NNT and TXNRD2), in which the receptor and its signaling cascade remain structurally intact but zona fasciculata cells progressively die from unchecked oxidative stress. Partial-function STAR mutations causing this phenotype (historically labeled FGD type 3) are distinct from the severe, combined adrenal-and-gonadal steroidogenic failure caused by classic STAR-null lipoid congenital adrenal hyperplasia. A third, mechanistically distinct route arises from biallelic loss-of-function mutations in MCM4, a component of the MCM2-7 replicative helicase essential for genome stability; the full MCM4-related phenotype additionally includes growth failure, increased chromosomal breakage, and natural killer (NK) cell deficiency (natural killer cell and glucocorticoid deficiency with DNA repair defect, NKGCD), extra-adrenal features that place it partly outside the isolated-FGD phenotype spectrum modeled here, so only its adrenocortical mechanism is curated on this entry. A substantial minority of FGD cases remain genetically unresolved even after accounting for MC2R, MRAP, STAR, NNT, TXNRD2, and MCM4. Lifelong glucocorticoid replacement corrects the cortisol deficiency and reverses the associated excessive linear growth seen in FGD type 1; mineralocorticoid replacement is not required.

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1
Inheritance
8
Pathophys.
7
Phenotypes
20
Pathograph
6
Genes
1
Medical Actions
5
Subtypes
3
Differentials
3
Models
1
Deep Research
🏷

Classifications

Harrison's Part
ENDOCRINOLOGY METABOLISM GENETICS ENVIRONMENT DISEASE
👪

Inheritance

1
Autosomal recessive inheritance HP:0000007
All molecularly defined forms of FGD (MC2R, MRAP, STAR, NNT, TXNRD2) are inherited in an autosomal recessive manner; affected individuals carry biallelic (homozygous or compound heterozygous) pathogenic variants, frequently in the setting of parental consanguinity.
Autosomal recessive inheritance
Show evidence (2 references)
PMID:15654338 SUPPORT Human Clinical
"Familial glucocorticoid deficiency (FGD), or hereditary unresponsiveness to adrenocorticotropin (ACTH; OMIM 202200), is an autosomal recessive disorder resulting from resistance to the action of ACTH on the adrenal cortex, which stimulates glucocorticoid production."
Establishes the autosomal recessive inheritance pattern and the core ACTH-resistance mechanism defining FGD.
PMID:8094489 SUPPORT Human Clinical
"Familial glucocorticoid deficiency is an uncommon disorder that appears to be due to congenital insensitivity or resistance to adrenocorticotropin (ACTH), and is usually inherited in an autosomal recessive pattern."
Describes the original MC2R kindred, confirming autosomal recessive segregation.
◆

Subtypes

5
FGD1 (MC2R-Related) MONDO:0024536
Caused by biallelic loss-of-function mutations in MC2R, the ACTH receptor itself, accounting for approximately 25% of FGD cases; the founding example is the c.220G>T (Ser74Ile) missense mutation in the second transmembrane domain. Most MC2R mutations are missense variants with varying degrees of impaired trafficking to the cell surface, often leaving some residual receptor function. Distinguished clinically from FGD2 by a later, more variable age of presentation (median 2.0 years) and unusually tall stature not seen in FGD2.
Show evidence (2 references)
PMID:8094489 SUPPORT Human Clinical
"The affected male proband showed a single base mutation, ser74-->ile, in the sequence coding for the second transmembrane domain of the ACTH receptor."
Describes the original MC2R point mutation identified as the cause of FGD1.
PMID:19558534 SUPPORT Human Clinical
"FGD resulting from MC2R mutations accounts for ∼25% of all FGD and is now known as FGD type 1"
Quantifies the proportion of FGD cases attributable to MC2R mutations.
FGD2 (MRAP-Related) MONDO:0011826
Caused by biallelic loss-of-function mutations in MRAP, the single-pass transmembrane accessory protein required for trafficking MC2R from the endoplasmic reticulum to the cell surface; accounts for approximately 20% of FGD cases. Reported MRAP mutations are predominantly splice-site or nonsense variants predicted to abolish the transmembrane domain essential for MC2R interaction, so MC2R is retained in the ER rather than reaching the plasma membrane. Presents earlier than FGD1 (median age 0.08 years) and, unlike FGD1, is not associated with tall stature.
Show evidence (3 references)
PMID:15654338 SUPPORT Human Clinical
"We show that MRAP interacts with MC2R and may have a role in the trafficking of MC2R from the endoplasmic reticulum to the cell surface."
Establishes MRAP's role as the MC2R trafficking chaperone whose loss causes FGD2.
PMID:19558534 SUPPORT Human Clinical
"and this accounts for ∼20% of FGD and is now known as FGD type 2."
Quantifies the proportion of FGD cases attributable to MRAP mutations.
PMID:19558534 SUPPORT Human Clinical
"MRAP is required in the earliest stages of MC2R processing and in the absence of MRAP protein, the receptor is retained within the ER."
Describes the ER-retention mechanism by which MRAP loss abolishes MC2R surface expression.
FGD3 (STAR-Related, Partial Function) MONDO:0012214
Originally defined by linkage of unexplained FGD (unlinked to MC2R or MRAP) to a locus on chromosome 8, subsequently resolved as certain partial-function missense mutations (e.g., R192C, R188C) in STAR, encoding the steroidogenic acute regulatory protein that mediates the rate-limiting transfer of cholesterol across mitochondrial membranes for steroidogenesis; accounts for approximately 5-10% of FGD. This is distinct from classic, complete STAR loss-of-function, which instead causes lipoid congenital adrenal hyperplasia with combined adrenal and gonadal steroidogenic failure and disordered sex development in 46,XY individuals; the partial-function FGD3 variants retain enough residual StAR activity in the adrenal to spare mineralocorticoid and gonadal steroidogenesis while cortisol production still fails.
Show evidence (3 references)
PMID:19773404 SUPPORT Human Clinical
"A locus on chromosome 8 has previously been linked to the disease in three families, but no underlying gene defect has to date been identified."
Documents the historical chromosome 8-linked, gene-unresolved status of FGD3 prior to STAR identification.
PMID:19773404 SUPPORT Human Clinical
"Mutations in STAR usually cause lipoid congenital adrenal hyperplasia, a disorder characterized by both gonadal and adrenal steroid deficiency. Our results demonstrate that certain mutations in STAR (R192C and the previously reported R188C) can present with a phenotype indistinguishable from..."
Establishes that specific partial-function STAR mutations cause an FGD-indistinguishable phenotype, distinct from classic lipoid CAH.
PMID:30817990 SUPPORT Human Clinical
"Primarily there are three established subtypes of the disease: FGD 1, FGD2 and FGD3 corresponding to mutations in the Melanocortin 2 receptor MC2R (25%), Melanocortin 2 receptor accessory protein MRAP (20%), and Steroidogenic acute regulatory protein STAR (5-10%) respectively."
Quantifies the proportion of FGD attributable to STAR (FGD3) alongside MC2R and MRAP.
FGD4 (NNT-Related) MONDO:0013874
Caused by biallelic loss-of-function mutations in NNT, encoding nicotinamide nucleotide transhydrogenase, an inner mitochondrial membrane enzyme that generates NADPH from the mitochondrial proton gradient; NADPH is required to regenerate reduced glutathione for detoxification of reactive oxygen species. Loss of NNT function causes oxidative-stress-driven adrenocortical cell apoptosis rather than a primary defect of ACTH receptor signaling, distinguishing this mechanistic route from FGD1-3.
Show evidence (2 references)
PMID:22634753 SUPPORT Human Clinical
"Using targeted exome sequencing, we identified mutations in NNT, an antioxidant defense gene, in individuals with familial glucocorticoid deficiency."
Establishes NNT loss-of-function mutations as a genetic cause of FGD.
PMID:22634753 SUPPORT In Vitro
"NNT knockdown in a human adrenocortical cell line resulted in impaired redox potential and increased reactive oxygen species (ROS) levels."
Human adrenocortical cell line data mechanistically links NNT loss to impaired redox homeostasis.
FGD5 (TXNRD2-Related) MONDO:0040502
Caused by biallelic loss-of-function mutations in TXNRD2, encoding the mitochondrial selenoprotein thioredoxin reductase 2, which uses NADPH (generated in part via NNT) to reduce thioredoxin as part of the mitochondrial antioxidant defense system. Identified in a consanguineous kindred with a homozygous stop-gain mutation causing complete absence of TXNRD2 protein; the first reported human disease caused by loss of any component of the thioredoxin antioxidant system. Mechanistically grouped with FGD4 (NNT) as an oxidative-stress route to adrenocortical failure, distinct from the ACTH-receptor-signaling routes (FGD1-3).
Show evidence (2 references)
PMID:24601690 SUPPORT Human Clinical
"A stop gain mutation, p.Y447X in TXNRD2, encoding the mitochondrial selenoprotein thioredoxin reductase 2 (TXNRD2) was identified and segregated with disease in this extended kindred."
Identifies the causal TXNRD2 mutation and its segregation with the FGD5 phenotype.
PMID:24601690 SUPPORT In Vitro
"TXNRD2 deficiency leads to impaired redox homeostasis in a human adrenocortical cell line."
Functional cell-line data linking TXNRD2 loss to impaired adrenocortical redox homeostasis.
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Pathophysiology

8
ACTH Receptor Complex Signaling Failure
MC2R (the ACTH receptor) requires its accessory protein MRAP for trafficking from the endoplasmic reticulum to the plasma membrane and for ACTH binding and Gs-coupled signal transduction. Biallelic loss-of-function variants in either MC2R (FGD1) or MRAP (FGD2) abolish or markedly reduce functional ACTH receptor signaling despite structurally intact adrenocortical cells.
cortical cell of adrenal gland CL:0002097 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cortical cell of adrenal gland (CL:0002097). CL:0002097 is a cell type from the Cell Ontology.
corticotropin receptor activity GO:0004978 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves corticotropin receptor activity (GO:0004978), qualified as loss of function. GO:0004978 is a molecular function from the Gene Ontology. ⇓ LOSS OF FUNCTION
Downstream
Impaired Adrenocortical Cortisol Biosynthesis Without functional ACTH receptor signaling, the cAMP-PKA cascade that normally drives steroidogenic enzyme expression in the zona fasciculata is not activated, so cortisol output fails despite an intact cell mass.
Show evidence (2 references)
PMID:15654338 SUPPORT Human Clinical
"We show that MRAP interacts with MC2R and may have a role in the trafficking of MC2R from the endoplasmic reticulum to the cell surface."
Establishes the MC2R-MRAP receptor complex and its dependence on MRAP for surface trafficking.
PMID:19558534 SUPPORT Human Clinical
"MRAP is required in the earliest stages of MC2R processing and in the absence of MRAP protein, the receptor is retained within the ER."
Describes the ER-retention mechanism underlying complete loss of receptor signaling in FGD2.
STAR-Mediated Cholesterol Transport Deficiency
STAR (steroidogenic acute regulatory protein) mediates the rate-limiting transfer of cholesterol from the outer to inner mitochondrial membrane in adrenocortical cells, the substrate-delivery step that precedes all steroidogenic enzyme reactions. Partial-function STAR missense mutations (FGD3) reduce but do not abolish this cholesterol transport, sufficiently to compromise cortisol output while sparing gonadal steroidogenesis and mineralocorticoid production (unlike complete STAR loss, which abolishes transport in both the adrenal and gonad).
cortical cell of adrenal gland CL:0002097 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cortical cell of adrenal gland (CL:0002097). CL:0002097 is a cell type from the Cell Ontology.
intracellular cholesterol transport GO:0032367 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased intracellular cholesterol transport (GO:0032367). GO:0032367 is a biological process from the Gene Ontology. ↓ DECREASED
cholesterol transfer activity GO:0120020 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased cholesterol transfer activity (GO:0120020). GO:0120020 is a molecular function from the Gene Ontology. ↓ DECREASED
Downstream
Impaired Adrenocortical Cortisol Biosynthesis Reduced mitochondrial cholesterol delivery limits substrate available to the steroidogenic enzyme cascade, lowering cortisol output.
Show evidence (1 reference)
PMID:19773404 SUPPORT Human Clinical
"We identified homozygous STAR mutations in this patient and his affected siblings."
Identifies homozygous STAR mutations underlying this FGD3 kindred.
Adrenocortical Mitochondrial Antioxidant Defense Failure
NNT (nicotinamide nucleotide transhydrogenase) uses the mitochondrial proton gradient to generate high concentrations of NADPH, which TXNRD2 (thioredoxin reductase 2) and glutathione peroxidases require to detoxify reactive oxygen species by maintaining a high reduced-to-oxidized glutathione (GSH/GSSG) ratio. Biallelic loss-of-function variants in either NNT (FGD4) or TXNRD2 (FGD5) impair this antioxidant axis specifically in adrenocortical mitochondria, without affecting ACTH receptor signaling itself.
cortical cell of adrenal gland CL:0002097 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cortical cell of adrenal gland (CL:0002097). CL:0002097 is a cell type from the Cell Ontology.
proton-translocating NAD(P)+ transhydrogenase activity GO:0008750 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves proton-translocating NAD(P)+ transhydrogenase activity (GO:0008750), qualified as loss of function. GO:0008750 is a molecular function from the Gene Ontology. ⇓ LOSS OF FUNCTION thioredoxin-disulfide reductase (NADPH) activity GO:0004791 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves thioredoxin-disulfide reductase (NADPH) activity (GO:0004791), qualified as loss of function. GO:0004791 is a molecular function from the Gene Ontology. ⇓ LOSS OF FUNCTION
Experimental models
NNT-knockdown human adrenocortical cell line CELL LINE NNT knockdown reproduces the redox-impairment step of the NNT-related mechanism directly in a human adrenocortical cell background.
TXNRD2-deficient human adrenocortical cell line CELL LINE TXNRD2 deficiency reproduces the redox-impairment step of the thioredoxin-dependent arm of the antioxidant-defense mechanism directly in a human adrenocortical cell background.
Downstream
Adrenocortical Oxidative Stress and Apoptosis Loss of NADPH-dependent glutathione/thioredoxin recycling capacity raises reactive oxygen species and lowers the GSH/GSSG ratio in adrenocortical mitochondria.
Show evidence (2 references)
PMID:22634753 SUPPORT Human Clinical
"Detoxification in mitochondria of reactive oxygen species (ROS) by glutathione peroxidases depends on this NADPH for regeneration of reduced glutathione (GSH) from oxidized glutathione (GSSG) to maintain a high GSH/GSSG ratio"
Describes the NADPH-dependent antioxidant mechanism disrupted by NNT loss.
PMID:24601690 SUPPORT In Vitro
"TXNRD2 deficiency leads to impaired redox homeostasis in a human adrenocortical cell line."
Confirms TXNRD2 loss also impairs adrenocortical redox homeostasis, mechanistically paralleling NNT loss.
Adrenocortical Oxidative Stress and Apoptosis
Unchecked accumulation of reactive oxygen species in adrenocortical mitochondria drives zona fasciculata cell apoptosis and progressive cell loss, a mechanistically distinct route to glucocorticoid deficiency from the receptor-signaling-failure forms (FGD1-3), since the ACTH receptor and its downstream signaling cascade remain structurally intact.
cortical cell of adrenal gland CL:0002097 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cortical cell of adrenal gland (CL:0002097). CL:0002097 is a cell type from the Cell Ontology.
cellular response to oxidative stress GO:0034599 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased cellular response to oxidative stress (GO:0034599). GO:0034599 is a biological process from the Gene Ontology. ↑ INCREASED
Animal models
Nnt-loss mouse Mouse recapitulates Nnt-loss mice show increased adrenocortical cell apoptosis and impaired glucocorticoid production, recapitulating the oxidative-stress-driven cell-loss mechanism proposed for human NNT-related FGD (FGD4).
Downstream
Impaired Adrenocortical Cortisol Biosynthesis Progressive loss of zona fasciculata cells reduces the functional steroidogenic cell mass available to synthesize cortisol.
Show evidence (1 reference)
PMID:24601690 SUPPORT Human Clinical
"Recently FGD cases caused by mutations in the mitochondrial antioxidant, nicotinamide nucleotide transhydrogenase, have highlighted the importance of redox regulation in steroidogenesis."
Frames oxidative-stress-driven adrenocortical failure as a distinct mechanistic class within FGD.
Adrenocortical Replicative Stress and Impaired Steroidogenic Cell Differentiation
MCM4 is part of the MCM2-7 complex, the core replicative helicase required for normal DNA replication and genome stability in eukaryotic cells. Biallelic loss-of-function MCM4 variants define a third mechanistic route to adrenocortical failure, distinct from both ACTH-receptor-signaling failure (FGD1-3) and oxidative-stress-driven apoptosis of mature steroidogenic cells (FGD4-5): Mcm4-depleted mouse adrenal cortex shows grossly abnormal morphology, with non-steroidogenic GATA4- and Gli1-positive cells persisting within the cortex and reducing the number of cells that differentiate into steroidogenic zona fasciculata cells.
cortical cell of adrenal gland CL:0002097 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cortical cell of adrenal gland (CL:0002097). CL:0002097 is a cell type from the Cell Ontology.
DNA replication GO:0006260 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves DNA replication (GO:0006260), qualified as loss of function. GO:0006260 is a biological process from the Gene Ontology. ⇓ LOSS OF FUNCTION
Downstream
Impaired Adrenocortical Cortisol Biosynthesis Fewer cells differentiate into steroidogenic zona fasciculata cells, reducing the functional cortisol-producing cell mass available for steroidogenesis.
Show evidence (2 references)
PMID:22354170 SUPPORT Human Clinical
"Since MCM4 is one part of a MCM2-7 complex recently confirmed as the replicative helicase essential for normal DNA replication and genome stability in all eukaryotes, it is possible that our patients may have an increased risk of neoplastic change."
Establishes MCM4's role in the replicative helicase complex, framing the replicative/genomic-stress mechanism as distinct from the receptor and redox routes.
PMID:23279877 SUPPORT Human Clinical
"These latest findings expand the spectrum of pathogenetic mechanisms causing adrenal disease and imply that the adrenal may be hypersensitive to replicative and oxidative stresses."
Review frames replicative stress (MCM4) alongside oxidative stress (NNT) as the two newly recognized non-receptor mechanistic routes in FGD.
Impaired Adrenocortical Cortisol Biosynthesis
Convergent endpoint of both mechanistic routes: whether ACTH signaling fails at the receptor (FGD1-3) or redox-competent zona fasciculata cells are progressively lost (FGD4-5), net cortisol output from the adrenal cortex falls, producing the shared biochemical and clinical phenotype of FGD.
Downstream
Loss of Cortisol-Mediated Negative Feedback and Compensatory ACTH Hypersecretion Failure of cortisol production removes the principal negative-feedback signal on the hypothalamic-pituitary-adrenal axis.
Decreased circulating cortisol level Impaired cortisol biosynthesis directly produces the low or undetectable serum cortisol that is the core biochemical phenotype of FGD, unresponsive to exogenous ACTH stimulation.
Hypoglycemia Cortisol is required for hepatic gluconeogenesis and counter-regulatory glucose defense, so impaired cortisol biosynthesis produces hypoglycemia, a presenting and potentially life-threatening feature.
Failure to thrive Cortisol deficiency impairs growth and metabolic homeostasis in infancy, producing failure to thrive as part of the classic presentation.
Recurrent or severe infections Loss of cortisol's role in immune and metabolic homeostasis increases susceptibility to recurrent or overwhelming infection, historically a cause of mortality in undiagnosed FGD.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
Summarizes the convergent biochemical phenotype of impaired cortisol biosynthesis across FGD subtypes.
Preserved Zona Glomerulosa Mineralocorticoid Production
The zona glomerulosa (aldosterone-producing layer of the adrenal cortex, UBERON:0002053) is regulated principally by the renin-angiotensin-potassium axis rather than by ACTH, so it is functionally spared in FGD even when the ACTH-dependent zona fasciculata (cortisol-producing layer) fails. This is the mechanistic basis for the normal plasma renin activity and serum aldosterone that distinguish FGD from combined-deficiency forms of primary adrenal insufficiency, such as autoimmune Addison disease, congenital adrenal hyperplasia, or classic (complete) STAR-null lipoid congenital adrenal hyperplasia, in which mineralocorticoid production is also lost.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
States the preserved-mineralocorticoid-production biochemical hallmark that distinguishes FGD from combined adrenal insufficiency.
Loss of Cortisol-Mediated Negative Feedback and Compensatory ACTH Hypersecretion
Absent cortisol negative feedback on the hypothalamus and pituitary corticotrophs drives markedly elevated plasma ACTH and other proopiomelanocortin (POMC)-derived peptides, including melanocyte-stimulating hormone activity, producing the characteristic generalized hyperpigmentation of FGD as well as the risk of hypoglycemia, failure to thrive, and susceptibility to infection that define the untreated clinical course.
Downstream
Hyperpigmentation Markedly elevated ACTH and other POMC-derived peptides, including melanocyte-stimulating hormone activity, act on melanocortin 1 receptors in melanocytes to produce generalized hyperpigmentation.
Increased circulating ACTH level Loss of cortisol-mediated negative feedback on the hypothalamic-pituitary axis is the direct cause of the markedly elevated plasma ACTH that defines this biochemical phenotype.
Show evidence (2 references)
PMID:15654338 SUPPORT Human Clinical
"Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood."
Documents the clinical consequences of unopposed cortisol deficiency if the compensatory HPA response is not corrected by treatment.
PMID:22634753 SUPPORT Human Clinical
"Patients typically present within the first few months of life with symptoms related to cortisol deficiency including recurrent illnesses/infections, hypoglycaemia, convulsions, failure to thrive and shock."
Documents the classic presenting symptom complex of FGD driven by cortisol deficiency.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Familial Glucocorticoid Deficiency Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

7
Immune 1
Recurrent or severe infections Recurrent infections HP:0002719 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Recurrent infections (HP:0002719). HP:0002719 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:15654338 SUPPORT Human Clinical
"Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood."
Documents overwhelming infection as a life-threatening consequence of untreated FGD.
Integument 1
Hyperpigmentation Hyperpigmentation of the skin HP:0000953 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hyperpigmentation of the skin (HP:0000953). HP:0000953 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"patients usually present with hypoglycaemia, seizure, jaundice, hyperpigmentation, failure to thrive and frequent or severe infections"
Lists hyperpigmentation among the classic presenting features of FGD.
Metabolism 1
Hypoglycemia VERY_FREQUENT HP:0001943 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypoglycemia (HP:0001943). HP:0001943 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:15654338 SUPPORT Human Clinical
"Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood."
Identifies hypoglycemia as a major, potentially fatal, consequence of untreated cortisol deficiency in FGD.
Growth 2
Failure to thrive HP:0001508 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Failure to thrive (HP:0001508). HP:0001508 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22634753 SUPPORT Human Clinical
"Patients typically present within the first few months of life with symptoms related to cortisol deficiency including recurrent illnesses/infections, hypoglycaemia, convulsions, failure to thrive and shock."
Lists failure to thrive among the classic early-life presenting symptoms of FGD.
Tall stature HP:0000098 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Tall stature (HP:0000098). HP:0000098 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:11012566 SUPPORT Human Clinical
"All patients demonstrated excessive linear growth over that predicted from parental indices and increased head circumference."
Documents excessive linear growth and macrocephaly in FGD patients (predominantly MC2R-mutation-positive) prior to treatment.
PMID:19558534 SUPPORT Human Clinical
"Tall stature is associated with mutations in MC2R but not in MRAP."
Establishes that tall stature specifically distinguishes FGD1 (MC2R) from FGD2 (MRAP).
Other 2
Increased circulating ACTH level HP:0003154 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Increased circulating ACTH level (HP:0003154). HP:0003154 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
Establishes elevated ACTH with low cortisol as the core biochemical phenotype.
Decreased circulating cortisol level HP:0008163 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Decreased circulating cortisol level (HP:0008163). HP:0008163 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"characterized by elevated plasma ACTH, and low or undetectable cortisol in the absence of overt mineralocorticoid deficiency"
Documents low/undetectable cortisol with preserved mineralocorticoid status as the defining biochemical phenotype.
🧬

Genetic Associations

6
MC2R (Loss-of-function)
Gene: MC2R hgnc:6930 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is MC2R (hgnc:6930). hgnc:6930 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (1 reference)
PMID:8094489 SUPPORT Human Clinical
"The affected male proband showed a single base mutation, ser74-->ile, in the sequence coding for the second transmembrane domain of the ACTH receptor."
Identifies the original MC2R point mutation causing FGD1.
MRAP (Loss-of-function)
Gene: MRAP hgnc:1304 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is MRAP (hgnc:1304). hgnc:1304 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (1 reference)
PMID:15654338 SUPPORT Human Clinical
"We show that MRAP interacts with MC2R and may have a role in the trafficking of MC2R from the endoplasmic reticulum to the cell surface."
Identifies MRAP as the causal gene of FGD2 and its mechanistic role.
STAR (Partial loss-of-function)
Gene: STAR hgnc:11359 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is STAR (hgnc:11359). hgnc:11359 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (1 reference)
PMID:19773404 SUPPORT Human Clinical
"We identified homozygous STAR mutations in this patient and his affected siblings."
Identifies homozygous STAR mutations as the cause of FGD3 in this kindred.
NNT (Loss-of-function)
Gene: NNT hgnc:7863 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is NNT (hgnc:7863). hgnc:7863 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (1 reference)
PMID:22634753 SUPPORT Human Clinical
"Using targeted exome sequencing, we identified mutations in NNT, an antioxidant defense gene, in individuals with familial glucocorticoid deficiency."
Confirms NNT as a causal gene in FGD.
TXNRD2 (Loss-of-function)
Gene: TXNRD2 hgnc:18155 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is TXNRD2 (hgnc:18155). hgnc:18155 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (1 reference)
PMID:24601690 SUPPORT Human Clinical
"A stop gain mutation, p.Y447X in TXNRD2, encoding the mitochondrial selenoprotein thioredoxin reductase 2 (TXNRD2) was identified and segregated with disease in this extended kindred."
Confirms TXNRD2 as a causal gene in FGD.
MCM4 (Loss-of-function)
Gene: MCM4 hgnc:6947 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is MCM4 (hgnc:6947). hgnc:6947 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (2 references)
PMID:22354170 SUPPORT Human Clinical
"Targeted exome sequencing in 8 patients identified a variant (c.71-1insG) in minichromosome maintenance-deficient 4 (MCM4) that was predicted to result in a severely truncated protein (p.Pro24ArgfsX4)."
Identifies the causal MCM4 variant in the founding FGD-like kindred.
PMID:23279877 SUPPORT Human Clinical
"Recently mutations in mini chromosome maintenance-deficient 4 homologue (MCM4) and nicotinamide nucleotide transhydrogenase (NNT), genes involved in DNA replication and antioxidant defence respectively, have been recognised in FGD cohorts."
Review frames MCM4 as a distinct, replicative-stress-based genetic cause recognised in FGD cohorts alongside the redox-based NNT route.
💊

Medical Actions

1
Hydrocortisone Replacement Therapy
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: cortisol CHEBI:17650 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses cortisol (CHEBI:17650). CHEBI:17650 is a therapeutic agent from Chemical Entities of Biological Interest.
Lifelong glucocorticoid replacement (typically hydrocortisone in children) corrects cortisol deficiency and is the mainstay of FGD treatment; unlike combined-deficiency primary adrenal insufficiency, mineralocorticoid replacement is not required because zona glomerulosa function is preserved. Adequate replacement also normalizes the excessive linear growth characteristic of untreated FGD type 1.
Mechanism Target:
RESTORES Impaired Adrenocortical Cortisol Biosynthesis — Exogenous hydrocortisone substitutes directly for the deficient endogenous cortisol, regardless of which upstream route (receptor signaling failure, oxidative or replicative adrenocortical stress) caused the biosynthetic failure.
Show evidence (1 reference)
PMID:15654338 SUPPORT Human Clinical
"Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood."
Establishes the life-saving necessity of glucocorticoid replacement in correcting the cortisol deficiency.
INHIBITS Loss of Cortisol-Mediated Negative Feedback and Compensatory ACTH Hypersecretion — Restoring circulating cortisol reinstates negative feedback on the hypothalamic-pituitary-adrenal axis, suppressing the compensatory ACTH hypersecretion and reversing the excessive linear growth it drives in FGD type 1.
Show evidence (1 reference)
PMID:11012566 SUPPORT Human Clinical
"Growth charts suggest that the excessive growth is reduced to normal following the introduction of glucocorticoid replacement."
Demonstrates that glucocorticoid replacement reverses the ACTH-driven excessive growth of FGD type 1, evidencing suppression of the upstream hypersecretion.
Show evidence (2 references)
PMID:11012566 SUPPORT Human Clinical
"Growth charts suggest that the excessive growth is reduced to normal following the introduction of glucocorticoid replacement."
Demonstrates the clinical benefit of glucocorticoid replacement in normalizing the excessive growth of FGD type 1.
PMID:15654338 SUPPORT Human Clinical
"Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood."
Establishes the life-saving necessity of glucocorticoid replacement in FGD.
🔬

Biochemical Markers

4
Serum Cortisol (Decreased)
Context: Low or undetectable basal serum cortisol, unresponsive to cosyntropin (synthetic ACTH) stimulation, reflecting the shared endocrine endpoint of all FGD subtypes.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"characterized by elevated plasma ACTH, and low or undetectable cortisol in the absence of overt mineralocorticoid deficiency"
Documents low/undetectable cortisol as a core biochemical finding of FGD.
Plasma ACTH (Increased)
Context: Markedly elevated plasma ACTH from loss of cortisol-mediated negative feedback; median plasma ACTH at presentation is similarly elevated in both FGD1 and FGD2 (1409 and 1250 ng/l respectively in one cohort).
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
Establishes markedly elevated plasma ACTH as a defining biochemical finding of FGD.
Plasma Renin Activity (Normal)
Context: Preserved (not elevated) plasma renin activity is a key discriminating feature of FGD versus combined glucocorticoid-and-mineralocorticoid forms of primary adrenal insufficiency, in which renin is compensatorily elevated. Reflects intact renin-angiotensin-dependent regulation of the zona glomerulosa despite ACTH-dependent zona fasciculata failure.
Pathograph Readouts
Readout Of Preserved Zona Glomerulosa Mineralocorticoid Production
Normal (non-elevated) renin distinguishes isolated FGD from combined-deficiency primary adrenal insufficiency, in which renin rises compensatorily.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"characterized by elevated plasma ACTH, and low or undetectable cortisol in the absence of overt mineralocorticoid deficiency"
Supports the absence of overt mineralocorticoid deficiency, of which renin is the primary regulator and biochemical readout.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
States the preserved mineralocorticoid axis (renin/aldosterone) that distinguishes FGD from combined-deficiency primary adrenal insufficiency.
Serum Aldosterone (Normal)
Context: Preserved (not decreased) serum aldosterone, the other half of the mineralocorticoid-sparing biochemical signature that discriminates FGD from combined-deficiency primary adrenal insufficiency.
Pathograph Readouts
Readout Of Preserved Zona Glomerulosa Mineralocorticoid Production
Normal (non-decreased) aldosterone distinguishes isolated FGD from combined-deficiency primary adrenal insufficiency.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
Directly states preserved mineralocorticoid (aldosterone) production.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
Documents preserved mineralocorticoid (aldosterone) production as characteristic of FGD.
📊

Prevalence

1
Worldwide
Unknown Rare
FGD is a rare disorder; no robust numeric population prevalence estimate is established. A 15-year single tertiary referral center series (1993-2008) identified only 164 patients referred with a clinical diagnosis of FGD across all genetic subtypes, consistent with rarity.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"One hundred and sixty-four patients were referred to us from 1993 to 2008 for genetic screening with a clinical diagnosis of FGD"
Quantifies the rarity of FGD via a long-running specialist referral cohort.
🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Familial Glucocorticoid Deficiency:

Triple A (Allgrove) Syndrome
Overlapping Features The classic clinical differential for FGD: also presents with ACTH-resistant primary adrenal insufficiency and preserved mineralocorticoid production, caused by biallelic AAAS variants (a nuclear pore complex protein), but is distinguished by the additional cardinal features of esophageal achalasia and alacrima, plus progressive neurological involvement not seen in isolated FGD.
Distinguishing Features
  • Esophageal achalasia is a defining feature of Triple A syndrome, absent in FGD.
  • Alacrima (deficient tear production) is a defining feature of Triple A syndrome, absent in FGD.
  • Progressive peripheral/central neuropathy or cerebellar ataxia occur in Triple A syndrome but not isolated FGD.
  • AAAS sequencing distinguishes the two when the clinical triad of Triple A syndrome is incomplete.
Show evidence (1 reference)
PMID:22634753 SUPPORT Human Clinical
"Of particular relevance to our patients is Triple A syndrome (OMIM 231550)"
The NNT/FGD4 discovery paper explicitly identifies Triple A syndrome as the closest relevant differential, sharing an oxidative-stress mechanistic theme.
Autoimmune Addison Disease and Other Combined-Deficiency Causes of Chronic Primary Adrenal Insufficiency Not Yet Curated MONDO:0100480
Overlapping Features Autoimmune Addison disease and other causes of combined-deficiency chronic primary adrenal insufficiency (e.g., adrenoleukodystrophy, adrenal hemorrhage, infiltrative or infectious adrenalitis) present with cortisol deficiency and hyperpigmentation similarly to FGD, but additionally lose zona glomerulosa (aldosterone) function, producing hyponatremia, hyperkalemia, salt-wasting, and compensatory hyperreninemia that are absent in FGD. FGD itself sits within the broader chronic primary adrenal insufficiency umbrella (see `parents`) as its isolated-glucocorticoid, genetic-only branch; this differential names the combined-deficiency causes within that same umbrella that must be excluded, of which autoimmune Addison disease (`kb/disorders/Addisons_Disease.yaml`) is the most common.
Distinguishing Features
  • Elevated plasma renin activity (compensatory hyperreninemia) occurs in combined-deficiency primary adrenal insufficiency but not FGD.
  • Decreased aldosterone (mineralocorticoid deficiency) occurs in combined-deficiency primary adrenal insufficiency but not FGD.
  • Hyponatremia, hyperkalemia, and salt-wasting occur in combined-deficiency primary adrenal insufficiency but not FGD.
Show evidence (1 reference)
PMID:19558534 SUPPORT Human Clinical
"characterized by elevated plasma ACTH, and low or undetectable cortisol in the absence of overt mineralocorticoid deficiency"
States the preserved-mineralocorticoid criterion used to exclude combined-deficiency primary adrenal insufficiency in the FGD diagnostic cohort.
Classic (STAR-Null) Lipoid Congenital Adrenal Hyperplasia
Overlapping Features Complete loss-of-function STAR mutations cause a severe, distinct disorder with combined adrenal and gonadal steroidogenic failure (glucocorticoid, mineralocorticoid, and sex steroid deficiency) and disordered sex development in 46,XY individuals, in contrast to the partial-function STAR mutations underlying FGD3, which spare mineralocorticoid and gonadal steroidogenesis.
Distinguishing Features
  • Combined mineralocorticoid deficiency (salt-wasting) occurs in classic lipoid congenital adrenal hyperplasia but not FGD3.
  • Disordered sex development in 46,XY individuals occurs in classic lipoid congenital adrenal hyperplasia but not FGD3.
Show evidence (1 reference)
PMID:19773404 SUPPORT Human Clinical
"Mutations in STAR usually cause lipoid congenital adrenal hyperplasia, a disorder characterized by both gonadal and adrenal steroid deficiency. Our results demonstrate that certain mutations in STAR (R192C and the previously reported R188C) can present with a phenotype indistinguishable from..."
Directly contrasts the combined-deficiency phenotype of classic STAR loss with the FGD-like phenotype of partial-function STAR mutations.
🧫

Experimental Models

2
NNT-knockdown human adrenocortical cell line CELL_LINE
Human adrenocortical cell line with NNT knocked down, used to test whether loss of NNT directly impairs mitochondrial redox homeostasis.
cortical cell of adrenal gland CL:0002097 Cell Ontology (CL) Relation: this experimental model uses this cell type This experimental model uses cortical cell of adrenal gland (CL:0002097). CL:0002097 is a cell type from the Cell Ontology.
Organism
human NCBITaxon:9606 NCBI Taxonomy (NCBITaxon) Relation: this experimental model is built in this organism This experimental model is built in human, annotated with Homo sapiens (NCBITaxon:9606). NCBITaxon:9606 is an organism from the NCBI Taxonomy.
Publication
PMID:22634753
Pathograph links
Adrenocortical Mitochondrial Antioxidant Defense Failure recapitulates fidelity: moderate NNT knockdown reproduces the redox-impairment step of the NNT-related mechanism directly in a human adrenocortical cell background.
Limitations: A cultured, likely immortalized/carcinoma-derived adrenocortical cell line lacks intact HPA-axis regulation, normal adrenal architecture, and the in vivo cellular turnover relevant to the chronic human disease course.
Readouts
Redox potential and reactive oxygen species levels
Direction: INCREASED
Interpretation: Increased ROS and impaired redox potential after NNT knockdown directly demonstrate the proposed biochemical mechanism of NNT-related adrenocortical failure.
Show evidence (1 reference)
PMID:22634753 SUPPORT In Vitro
"NNT knockdown in a human adrenocortical cell line resulted in impaired redox potential and increased reactive oxygen species (ROS) levels."
Reports the redox potential and ROS measurements behind this readout.
Show evidence (1 reference)
PMID:22634753 SUPPORT In Vitro
"NNT knockdown in a human adrenocortical cell line resulted in impaired redox potential and increased reactive oxygen species (ROS) levels."
Supports treating the NNT-knockdown cell line as informative for the antioxidant-defense-failure node.
TXNRD2-deficient human adrenocortical cell line CELL_LINE
Human adrenocortical cell line with TXNRD2 deficiency, used to test whether loss of TXNRD2 directly impairs mitochondrial redox homeostasis, paralleling the NNT-knockdown system.
cortical cell of adrenal gland CL:0002097 Cell Ontology (CL) Relation: this experimental model uses this cell type This experimental model uses cortical cell of adrenal gland (CL:0002097). CL:0002097 is a cell type from the Cell Ontology.
Organism
human NCBITaxon:9606 NCBI Taxonomy (NCBITaxon) Relation: this experimental model is built in this organism This experimental model is built in human, annotated with Homo sapiens (NCBITaxon:9606). NCBITaxon:9606 is an organism from the NCBI Taxonomy.
Publication
PMID:24601690
Pathograph links
Adrenocortical Mitochondrial Antioxidant Defense Failure recapitulates fidelity: moderate TXNRD2 deficiency reproduces the redox-impairment step of the thioredoxin-dependent arm of the antioxidant-defense mechanism directly in a human adrenocortical cell background.
Limitations: A cultured, likely immortalized/carcinoma-derived adrenocortical cell line lacks intact HPA-axis regulation, normal adrenal architecture, and the in vivo cellular turnover relevant to the chronic human disease course.
Readouts
Redox homeostasis
Direction: ALTERED
Interpretation: Impaired redox homeostasis after TXNRD2 loss directly demonstrates the proposed biochemical mechanism of TXNRD2-related adrenocortical failure, mechanistically paralleling NNT loss.
Show evidence (1 reference)
PMID:24601690 SUPPORT In Vitro
"TXNRD2 deficiency leads to impaired redox homeostasis in a human adrenocortical cell line."
Reports the redox homeostasis measurement behind this readout.
Show evidence (1 reference)
PMID:24601690 SUPPORT In Vitro
"TXNRD2 deficiency leads to impaired redox homeostasis in a human adrenocortical cell line."
Supports treating the TXNRD2-deficient cell line as informative for the antioxidant-defense-failure node.
🐁

Animal Models

1
Nnt-loss mouse
Mice lacking functional Nnt were used to test whether loss of this NADPH-generating antioxidant enzyme reproduces the oxidative-stress route to adrenocortical failure identified in human FGD4 (NNT-related FGD).
Species
Mouse
Genotype
Nnt loss-of-function (C57BL/6J-background Nnt-deficient line)
Publication
PMID:22634753
Pathograph links
Adrenocortical Oxidative Stress and Apoptosis recapitulates fidelity: moderate Nnt-loss mice show increased adrenocortical cell apoptosis and impaired glucocorticoid production, recapitulating the oxidative-stress-driven cell-loss mechanism proposed for human NNT-related FGD (FGD4).
Limitations: The widely used C57BL/6J substrain carries a spontaneous Nnt deletion, so mouse adrenal zonation, steroidogenic regulation, and lifespan differ from human; the mouse data establish increased apoptosis and reduced glucocorticoid output but do not by themselves reproduce the full human FGD4 phenotype (e.g., the specific hyperpigmentation/ACTH-resistance presentation).
Readouts
Adrenocortical cell apoptosis
Direction: INCREASED
Interpretation: Increased apoptosis in Nnt-deficient mouse adrenal cortex supports oxidative stress as the driver of zona fasciculata cell loss in this mechanistic route.
Show evidence (1 reference)
PMID:22634753 SUPPORT Model Organism
"In mice with Nnt loss, higher levels of adrenocortical cell apoptosis and impaired glucocorticoid production were observed."
Reports the apoptosis and glucocorticoid-output measurements behind this readout.
Show evidence (1 reference)
PMID:22634753 SUPPORT Model Organism
"In mice with Nnt loss, higher levels of adrenocortical cell apoptosis and impaired glucocorticoid production were observed."
Supports treating the Nnt-loss mouse as informative for the oxidative-stress-driven adrenocortical failure node.
{ }

Source YAML

click to show 
name: Familial Glucocorticoid Deficiency
creation_date: "2026-08-26T00:00:00Z"
category: Mendelian
synonyms:
- Hereditary unresponsiveness to ACTH
- Familial ACTH resistance
- ACTH resistance syndrome
- Isolated glucocorticoid deficiency
- GCCD
description: >-
  Familial glucocorticoid deficiency (FGD) is a genetically heterogeneous
  group of autosomal recessive primary adrenal insufficiency disorders
  characterized by isolated failure of cortisol production in response to
  adrenocorticotropic hormone (ACTH), with classically preserved
  mineralocorticoid (aldosterone) secretion, because the aldosterone-producing
  zona glomerulosa is regulated principally by the renin-angiotensin system
  rather than by ACTH. Affected infants and children present with
  hypoglycemia, generalized hyperpigmentation (driven by markedly elevated
  ACTH and other POMC-derived peptides), failure to thrive, and recurrent or
  severe infections; unlike combined glucocorticoid-and-mineralocorticoid
  primary adrenal insufficiency, salt-wasting, hyponatremia, and hyperkalemia
  are characteristically absent. Two mechanistically distinct routes converge
  on the same endocrine endpoint: failure of ACTH receptor signaling itself
  (MC2R, the ACTH receptor, and its obligate trafficking chaperone MRAP,
  together accounting for roughly 45% of cases, plus partial-function
  mutations in STAR, the rate-limiting cholesterol-transport step of
  steroidogenesis) versus adrenocortical cell loss from failure of
  mitochondrial antioxidant defense (NNT and TXNRD2), in which the receptor
  and its signaling cascade remain structurally intact but zona fasciculata
  cells progressively die from unchecked oxidative stress. Partial-function
  STAR mutations causing this phenotype (historically labeled FGD type 3) are
  distinct from the severe, combined adrenal-and-gonadal steroidogenic
  failure caused by classic STAR-null lipoid congenital adrenal hyperplasia. A
  third, mechanistically distinct route arises from biallelic loss-of-function
  mutations in MCM4, a component of the MCM2-7 replicative helicase essential
  for genome stability; the full MCM4-related phenotype additionally includes
  growth failure, increased chromosomal breakage, and natural killer (NK) cell
  deficiency (natural killer cell and glucocorticoid deficiency with DNA
  repair defect, NKGCD), extra-adrenal features that place it partly outside
  the isolated-FGD phenotype spectrum modeled here, so only its adrenocortical
  mechanism is curated on this entry. A substantial minority of FGD cases
  remain genetically unresolved even after accounting for MC2R, MRAP, STAR,
  NNT, TXNRD2, and MCM4. Lifelong glucocorticoid replacement corrects the
  cortisol deficiency and reverses the associated excessive linear growth seen
  in FGD type 1; mineralocorticoid replacement is not required.
disease_term:
  preferred_term: familial glucocorticoid deficiency
  term:
    id: MONDO:0008733
    label: familial glucocorticoid deficiency
parents:
- Adrenal Insufficiency
- Chronic Primary Adrenal Insufficiency
classifications:
  harrisons_chapter:
  - classification_value: ENDOCRINOLOGY_METABOLISM
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
inheritance:
- name: Autosomal recessive inheritance
  description: >-
    All molecularly defined forms of FGD (MC2R, MRAP, STAR, NNT, TXNRD2) are
    inherited in an autosomal recessive manner; affected individuals carry
    biallelic (homozygous or compound heterozygous) pathogenic variants,
    frequently in the setting of parental consanguinity.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:15654338
    reference_title: "Mutations in MRAP, encoding a new interacting partner of the ACTH receptor, cause familial glucocorticoid deficiency type 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Familial glucocorticoid deficiency (FGD), or hereditary unresponsiveness to adrenocorticotropin (ACTH; OMIM 202200), is an autosomal recessive disorder resulting from resistance to the action of ACTH on the adrenal cortex, which stimulates glucocorticoid production."
    explanation: Establishes the autosomal recessive inheritance pattern and the core ACTH-resistance mechanism defining FGD.
  - reference: PMID:8094489
    reference_title: "Familial glucocorticoid deficiency associated with point mutation in the adrenocorticotropin receptor."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Familial glucocorticoid deficiency is an uncommon disorder that appears to be due to congenital insensitivity or resistance to adrenocorticotropin (ACTH), and is usually inherited in an autosomal recessive pattern."
    explanation: Describes the original MC2R kindred, confirming autosomal recessive segregation.
prevalence:
- population: Worldwide
  measure_type: UNKNOWN
  prevalence_class: RARE
  notes: >-
    FGD is a rare disorder; no robust numeric population prevalence estimate
    is established. A 15-year single tertiary referral center series
    (1993-2008) identified only 164 patients referred with a clinical
    diagnosis of FGD across all genetic subtypes, consistent with rarity.
  evidence:
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "One hundred and sixty-four patients were referred to us from 1993 to 2008 for genetic screening with a clinical diagnosis of FGD"
    explanation: Quantifies the rarity of FGD via a long-running specialist referral cohort.
has_subtypes:
- name: FGD1
  display_name: FGD1 (MC2R-Related)
  subtype_term:
    preferred_term: glucocorticoid deficiency 1
    term:
      id: MONDO:0024536
      label: glucocorticoid deficiency 1
  description: >-
    Caused by biallelic loss-of-function mutations in MC2R, the ACTH receptor
    itself, accounting for approximately 25% of FGD cases; the founding
    example is the c.220G>T (Ser74Ile) missense mutation in the second
    transmembrane domain. Most MC2R mutations are missense variants with
    varying degrees of impaired trafficking to the cell surface, often
    leaving some residual receptor function. Distinguished clinically from
    FGD2 by a later, more variable age of presentation (median 2.0 years) and
    unusually tall stature not seen in FGD2.
  evidence:
  - reference: PMID:8094489
    reference_title: "Familial glucocorticoid deficiency associated with point mutation in the adrenocorticotropin receptor."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The affected male proband showed a single base mutation, ser74-->ile, in the sequence coding for the second transmembrane domain of the ACTH receptor."
    explanation: Describes the original MC2R point mutation identified as the cause of FGD1.
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "FGD resulting from MC2R mutations accounts for ∼25% of all FGD and is now known as FGD type 1"
    explanation: Quantifies the proportion of FGD cases attributable to MC2R mutations.
- name: FGD2
  display_name: FGD2 (MRAP-Related)
  subtype_term:
    preferred_term: glucocorticoid deficiency 2
    term:
      id: MONDO:0011826
      label: glucocorticoid deficiency 2
  description: >-
    Caused by biallelic loss-of-function mutations in MRAP, the single-pass
    transmembrane accessory protein required for trafficking MC2R from the
    endoplasmic reticulum to the cell surface; accounts for approximately
    20% of FGD cases. Reported MRAP mutations are predominantly splice-site
    or nonsense variants predicted to abolish the transmembrane domain
    essential for MC2R interaction, so MC2R is retained in the ER rather than
    reaching the plasma membrane. Presents earlier than FGD1 (median age 0.08
    years) and, unlike FGD1, is not associated with tall stature.
  evidence:
  - reference: PMID:15654338
    reference_title: "Mutations in MRAP, encoding a new interacting partner of the ACTH receptor, cause familial glucocorticoid deficiency type 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We show that MRAP interacts with MC2R and may have a role in the trafficking of MC2R from the endoplasmic reticulum to the cell surface."
    explanation: Establishes MRAP's role as the MC2R trafficking chaperone whose loss causes FGD2.
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "and this accounts for ∼20% of FGD and is now known as FGD type 2."
    explanation: Quantifies the proportion of FGD cases attributable to MRAP mutations.
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "MRAP is required in the earliest stages of MC2R processing and in the absence of MRAP protein, the receptor is retained within the ER."
    explanation: Describes the ER-retention mechanism by which MRAP loss abolishes MC2R surface expression.
- name: FGD3
  display_name: FGD3 (STAR-Related, Partial Function)
  subtype_term:
    preferred_term: glucocorticoid deficiency 3
    term:
      id: MONDO:0012214
      label: glucocorticoid deficiency 3
  description: >-
    Originally defined by linkage of unexplained FGD (unlinked to MC2R or
    MRAP) to a locus on chromosome 8, subsequently resolved as certain
    partial-function missense mutations (e.g., R192C, R188C) in STAR,
    encoding the steroidogenic acute regulatory protein that mediates the
    rate-limiting transfer of cholesterol across mitochondrial membranes for
    steroidogenesis; accounts for approximately 5-10% of FGD. This is
    distinct from classic, complete STAR loss-of-function, which instead
    causes lipoid congenital adrenal hyperplasia with combined adrenal and
    gonadal steroidogenic failure and disordered sex development in 46,XY
    individuals; the partial-function FGD3 variants retain enough residual
    StAR activity in the adrenal to spare mineralocorticoid and gonadal
    steroidogenesis while cortisol production still fails.
  evidence:
  - reference: PMID:19773404
    reference_title: "Nonclassic lipoid congenital adrenal hyperplasia masquerading as familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A locus on chromosome 8 has previously been linked to the disease in three families, but no underlying gene defect has to date been identified."
    explanation: Documents the historical chromosome 8-linked, gene-unresolved status of FGD3 prior to STAR identification.
  - reference: PMID:19773404
    reference_title: "Nonclassic lipoid congenital adrenal hyperplasia masquerading as familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in STAR usually cause lipoid congenital adrenal hyperplasia, a disorder characterized by both gonadal and adrenal steroid deficiency. Our results demonstrate that certain mutations in STAR (R192C and the previously reported R188C) can present with a phenotype indistinguishable from that seen in FGD."
    explanation: Establishes that specific partial-function STAR mutations cause an FGD-indistinguishable phenotype, distinct from classic lipoid CAH.
  - reference: PMID:30817990
    reference_title: "Isolated glucocorticoid deficiency: Genetic causes and animal models."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Primarily there are three established subtypes of the disease: FGD 1, FGD2 and FGD3 corresponding to mutations in the Melanocortin 2 receptor MC2R (25%), Melanocortin 2 receptor accessory protein MRAP (20%), and Steroidogenic acute regulatory protein STAR (5-10%) respectively."
    explanation: Quantifies the proportion of FGD attributable to STAR (FGD3) alongside MC2R and MRAP.
- name: FGD4
  display_name: FGD4 (NNT-Related)
  subtype_term:
    preferred_term: glucocorticoid deficiency 4
    term:
      id: MONDO:0013874
      label: glucocorticoid deficiency 4
  description: >-
    Caused by biallelic loss-of-function mutations in NNT, encoding
    nicotinamide nucleotide transhydrogenase, an inner mitochondrial membrane
    enzyme that generates NADPH from the mitochondrial proton gradient; NADPH
    is required to regenerate reduced glutathione for detoxification of
    reactive oxygen species. Loss of NNT function causes oxidative-stress-driven
    adrenocortical cell apoptosis rather than a primary defect of ACTH
    receptor signaling, distinguishing this mechanistic route from FGD1-3.
  evidence:
  - reference: PMID:22634753
    reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Using targeted exome sequencing, we identified mutations in NNT, an antioxidant defense gene, in individuals with familial glucocorticoid deficiency."
    explanation: Establishes NNT loss-of-function mutations as a genetic cause of FGD.
  - reference: PMID:22634753
    reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "NNT knockdown in a human adrenocortical cell line resulted in impaired redox potential and increased reactive oxygen species (ROS) levels."
    explanation: Human adrenocortical cell line data mechanistically links NNT loss to impaired redox homeostasis.
- name: FGD5
  display_name: FGD5 (TXNRD2-Related)
  subtype_term:
    preferred_term: glucocorticoid deficiency 5
    term:
      id: MONDO:0040502
      label: glucocorticoid deficiency 5
  description: >-
    Caused by biallelic loss-of-function mutations in TXNRD2, encoding the
    mitochondrial selenoprotein thioredoxin reductase 2, which uses NADPH
    (generated in part via NNT) to reduce thioredoxin as part of the
    mitochondrial antioxidant defense system. Identified in a consanguineous
    kindred with a homozygous stop-gain mutation causing complete absence of
    TXNRD2 protein; the first reported human disease caused by loss of any
    component of the thioredoxin antioxidant system. Mechanistically grouped
    with FGD4 (NNT) as an oxidative-stress route to adrenocortical failure,
    distinct from the ACTH-receptor-signaling routes (FGD1-3).
  evidence:
  - reference: PMID:24601690
    reference_title: "Thioredoxin Reductase 2 (TXNRD2) mutation associated with familial glucocorticoid deficiency (FGD)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A stop gain mutation, p.Y447X in TXNRD2, encoding the mitochondrial selenoprotein thioredoxin reductase 2 (TXNRD2) was identified and segregated with disease in this extended kindred."
    explanation: Identifies the causal TXNRD2 mutation and its segregation with the FGD5 phenotype.
  - reference: PMID:24601690
    reference_title: "Thioredoxin Reductase 2 (TXNRD2) mutation associated with familial glucocorticoid deficiency (FGD)."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TXNRD2 deficiency leads to impaired redox homeostasis in a human adrenocortical cell line."
    explanation: Functional cell-line data linking TXNRD2 loss to impaired adrenocortical redox homeostasis.
genetic:
- name: MC2R
  gene_term:
    preferred_term: MC2R
    term:
      id: hgnc:6930
      label: MC2R
  association: Loss-of-function
  presence: Positive
  subtype: FGD1
  evidence:
  - reference: PMID:8094489
    reference_title: "Familial glucocorticoid deficiency associated with point mutation in the adrenocorticotropin receptor."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The affected male proband showed a single base mutation, ser74-->ile, in the sequence coding for the second transmembrane domain of the ACTH receptor."
    explanation: Identifies the original MC2R point mutation causing FGD1.
  case_fractions:
  - population: UK tertiary referral cohort (FGD screening, 1993-2008)
    case_fraction_percent: 25
    notes: Most common single genetic cause of FGD.
    evidence:
    - reference: PMID:19558534
      reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "FGD resulting from MC2R mutations accounts for ∼25% of all FGD and is now known as FGD type 1"
      explanation: Quantifies the MC2R (FGD1) share of FGD cases.
- name: MRAP
  gene_term:
    preferred_term: MRAP
    term:
      id: hgnc:1304
      label: MRAP
  association: Loss-of-function
  presence: Positive
  subtype: FGD2
  evidence:
  - reference: PMID:15654338
    reference_title: "Mutations in MRAP, encoding a new interacting partner of the ACTH receptor, cause familial glucocorticoid deficiency type 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We show that MRAP interacts with MC2R and may have a role in the trafficking of MC2R from the endoplasmic reticulum to the cell surface."
    explanation: Identifies MRAP as the causal gene of FGD2 and its mechanistic role.
  case_fractions:
  - population: UK tertiary referral cohort (FGD screening, 1993-2008)
    case_fraction_percent: 20
    evidence:
    - reference: PMID:19558534
      reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "and this accounts for ∼20% of FGD and is now known as FGD type 2."
      explanation: Quantifies the MRAP (FGD2) share of FGD cases.
- name: STAR
  gene_term:
    preferred_term: STAR
    term:
      id: hgnc:11359
      label: STAR
  association: Partial loss-of-function
  presence: Positive
  subtype: FGD3
  notes: >-
    Only specific partial-function missense mutations (e.g., R192C, R188C)
    present as isolated FGD; complete STAR loss instead causes lipoid
    congenital adrenal hyperplasia, a distinct and more severe disorder.
  evidence:
  - reference: PMID:19773404
    reference_title: "Nonclassic lipoid congenital adrenal hyperplasia masquerading as familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified homozygous STAR mutations in this patient and his affected siblings."
    explanation: Identifies homozygous STAR mutations as the cause of FGD3 in this kindred.
  case_fractions:
  - population: FGD referral cohorts (multi-center)
    case_fraction_low: 5
    case_fraction_high: 10
    evidence:
    - reference: PMID:30817990
      reference_title: "Isolated glucocorticoid deficiency: Genetic causes and animal models."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Primarily there are three established subtypes of the disease: FGD 1, FGD2 and FGD3 corresponding to mutations in the Melanocortin 2 receptor MC2R (25%), Melanocortin 2 receptor accessory protein MRAP (20%), and Steroidogenic acute regulatory protein STAR (5-10%) respectively."
      explanation: Quantifies the STAR (FGD3) share of FGD cases.
- name: NNT
  gene_term:
    preferred_term: NNT
    term:
      id: hgnc:7863
      label: NNT
  association: Loss-of-function
  presence: Positive
  subtype: FGD4
  evidence:
  - reference: PMID:22634753
    reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Using targeted exome sequencing, we identified mutations in NNT, an antioxidant defense gene, in individuals with familial glucocorticoid deficiency."
    explanation: Confirms NNT as a causal gene in FGD.
- name: TXNRD2
  gene_term:
    preferred_term: TXNRD2
    term:
      id: hgnc:18155
      label: TXNRD2
  association: Loss-of-function
  presence: Positive
  subtype: FGD5
  evidence:
  - reference: PMID:24601690
    reference_title: "Thioredoxin Reductase 2 (TXNRD2) mutation associated with familial glucocorticoid deficiency (FGD)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A stop gain mutation, p.Y447X in TXNRD2, encoding the mitochondrial selenoprotein thioredoxin reductase 2 (TXNRD2) was identified and segregated with disease in this extended kindred."
    explanation: Confirms TXNRD2 as a causal gene in FGD.
- name: MCM4
  gene_term:
    preferred_term: MCM4
    term:
      id: hgnc:6947
      label: MCM4
  association: Loss-of-function
  presence: Positive
  notes: >-
    Identified in a genetically isolated Irish population with an FGD-like
    presentation additionally featuring growth failure, increased chromosomal
    breakage, and NK cell deficiency (natural killer cell and glucocorticoid
    deficiency with DNA repair defect, NKGCD; OMIM:609981, MONDO:0012383).
    MONDO models the full NKGCD phenotype as a distinct immunodeficiency
    disease rather than as a numbered subtype in the FGD1-5 series, so it is
    not curated here as a `has_subtypes` entry; only its adrenocortical
    (replicative-stress) mechanism is represented on this entry's
    pathophysiology graph.
  evidence:
  - reference: PMID:22354170
    reference_title: "MCM4 mutation causes adrenal failure, short stature, and natural killer cell deficiency in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Targeted exome sequencing in 8 patients identified a variant (c.71-1insG) in minichromosome maintenance-deficient 4 (MCM4) that was predicted to result in a severely truncated protein (p.Pro24ArgfsX4)."
    explanation: Identifies the causal MCM4 variant in the founding FGD-like kindred.
  - reference: PMID:23279877
    reference_title: "Familial glucocorticoid deficiency: New genes and mechanisms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recently mutations in mini chromosome maintenance-deficient 4 homologue (MCM4) and nicotinamide nucleotide transhydrogenase (NNT), genes involved in DNA replication and antioxidant defence respectively, have been recognised in FGD cohorts."
    explanation: Review frames MCM4 as a distinct, replicative-stress-based genetic cause recognised in FGD cohorts alongside the redox-based NNT route.
pathophysiology:
- name: ACTH Receptor Complex Signaling Failure
  biological_scale: MOLECULAR
  description: >-
    MC2R (the ACTH receptor) requires its accessory protein MRAP for
    trafficking from the endoplasmic reticulum to the plasma membrane and for
    ACTH binding and Gs-coupled signal transduction. Biallelic loss-of-function
    variants in either MC2R (FGD1) or MRAP (FGD2) abolish or markedly reduce
    functional ACTH receptor signaling despite structurally intact
    adrenocortical cells.
  molecular_functions:
  - preferred_term: corticotropin receptor activity
    term:
      id: GO:0004978
      label: corticotropin receptor activity
    modifier: LOSS_OF_FUNCTION
  cell_types:
  - preferred_term: cortical cell of adrenal gland
    term:
      id: CL:0002097
      label: cortical cell of adrenal gland
  downstream:
  - target: Impaired Adrenocortical Cortisol Biosynthesis
    description: >-
      Without functional ACTH receptor signaling, the cAMP-PKA cascade that
      normally drives steroidogenic enzyme expression in the zona fasciculata
      is not activated, so cortisol output fails despite an intact cell mass.
    evidence:
    - reference: PMID:19558534
      reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
      explanation: Documents the biochemical signature (high ACTH, low cortisol, preserved mineralocorticoid) resulting from ACTH receptor signaling failure.
  evidence:
  - reference: PMID:15654338
    reference_title: "Mutations in MRAP, encoding a new interacting partner of the ACTH receptor, cause familial glucocorticoid deficiency type 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We show that MRAP interacts with MC2R and may have a role in the trafficking of MC2R from the endoplasmic reticulum to the cell surface."
    explanation: Establishes the MC2R-MRAP receptor complex and its dependence on MRAP for surface trafficking.
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "MRAP is required in the earliest stages of MC2R processing and in the absence of MRAP protein, the receptor is retained within the ER."
    explanation: Describes the ER-retention mechanism underlying complete loss of receptor signaling in FGD2.
- name: STAR-Mediated Cholesterol Transport Deficiency
  biological_scale: MOLECULAR
  description: >-
    STAR (steroidogenic acute regulatory protein) mediates the rate-limiting
    transfer of cholesterol from the outer to inner mitochondrial membrane in
    adrenocortical cells, the substrate-delivery step that precedes all
    steroidogenic enzyme reactions. Partial-function STAR missense mutations
    (FGD3) reduce but do not abolish this cholesterol transport, sufficiently
    to compromise cortisol output while sparing gonadal steroidogenesis and
    mineralocorticoid production (unlike complete STAR loss, which abolishes
    transport in both the adrenal and gonad).
  molecular_functions:
  - preferred_term: cholesterol transfer activity
    term:
      id: GO:0120020
      label: cholesterol transfer activity
    modifier: DECREASED
  biological_processes:
  - preferred_term: intracellular cholesterol transport
    term:
      id: GO:0032367
      label: intracellular cholesterol transport
    modifier: DECREASED
  cell_types:
  - preferred_term: cortical cell of adrenal gland
    term:
      id: CL:0002097
      label: cortical cell of adrenal gland
  downstream:
  - target: Impaired Adrenocortical Cortisol Biosynthesis
    description: >-
      Reduced mitochondrial cholesterol delivery limits substrate available
      to the steroidogenic enzyme cascade, lowering cortisol output.
    evidence:
    - reference: PMID:19773404
      reference_title: "Nonclassic lipoid congenital adrenal hyperplasia masquerading as familial glucocorticoid deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Mutations in STAR usually cause lipoid congenital adrenal hyperplasia, a disorder characterized by both gonadal and adrenal steroid deficiency. Our results demonstrate that certain mutations in STAR (R192C and the previously reported R188C) can present with a phenotype indistinguishable from that seen in FGD."
      explanation: Links partial-function STAR mutations to an FGD-type isolated cortisol deficiency, distinct from complete STAR loss.
  evidence:
  - reference: PMID:19773404
    reference_title: "Nonclassic lipoid congenital adrenal hyperplasia masquerading as familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified homozygous STAR mutations in this patient and his affected siblings."
    explanation: Identifies homozygous STAR mutations underlying this FGD3 kindred.
- name: Adrenocortical Mitochondrial Antioxidant Defense Failure
  biological_scale: MOLECULAR
  description: >-
    NNT (nicotinamide nucleotide transhydrogenase) uses the mitochondrial
    proton gradient to generate high concentrations of NADPH, which TXNRD2
    (thioredoxin reductase 2) and glutathione peroxidases require to detoxify
    reactive oxygen species by maintaining a high reduced-to-oxidized
    glutathione (GSH/GSSG) ratio. Biallelic loss-of-function variants in
    either NNT (FGD4) or TXNRD2 (FGD5) impair this antioxidant axis
    specifically in adrenocortical mitochondria, without affecting ACTH
    receptor signaling itself.
  molecular_functions:
  - preferred_term: proton-translocating NAD(P)+ transhydrogenase activity
    term:
      id: GO:0008750
      label: proton-translocating NAD(P)+ transhydrogenase activity
    modifier: LOSS_OF_FUNCTION
  - preferred_term: thioredoxin-disulfide reductase (NADPH) activity
    term:
      id: GO:0004791
      label: thioredoxin-disulfide reductase (NADPH) activity
    modifier: LOSS_OF_FUNCTION
  cell_types:
  - preferred_term: cortical cell of adrenal gland
    term:
      id: CL:0002097
      label: cortical cell of adrenal gland
  downstream:
  - target: Adrenocortical Oxidative Stress and Apoptosis
    description: >-
      Loss of NADPH-dependent glutathione/thioredoxin recycling capacity
      raises reactive oxygen species and lowers the GSH/GSSG ratio in
      adrenocortical mitochondria.
    evidence:
    - reference: PMID:22634753
      reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "NNT knockdown in a human adrenocortical cell line resulted in impaired redox potential and increased reactive oxygen species (ROS) levels."
      explanation: Human adrenocortical cell-line knockdown directly links NNT loss to increased ROS and impaired redox potential.
  evidence:
  - reference: PMID:22634753
    reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Detoxification in mitochondria of reactive oxygen species (ROS) by glutathione peroxidases depends on this NADPH for regeneration of reduced glutathione (GSH) from oxidized glutathione (GSSG) to maintain a high GSH/GSSG ratio"
    explanation: Describes the NADPH-dependent antioxidant mechanism disrupted by NNT loss.
  - reference: PMID:24601690
    reference_title: "Thioredoxin Reductase 2 (TXNRD2) mutation associated with familial glucocorticoid deficiency (FGD)."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TXNRD2 deficiency leads to impaired redox homeostasis in a human adrenocortical cell line."
    explanation: Confirms TXNRD2 loss also impairs adrenocortical redox homeostasis, mechanistically paralleling NNT loss.
- name: Adrenocortical Oxidative Stress and Apoptosis
  biological_scale: CELLULAR
  description: >-
    Unchecked accumulation of reactive oxygen species in adrenocortical
    mitochondria drives zona fasciculata cell apoptosis and progressive cell
    loss, a mechanistically distinct route to glucocorticoid deficiency from
    the receptor-signaling-failure forms (FGD1-3), since the ACTH receptor
    and its downstream signaling cascade remain structurally intact.
  biological_processes:
  - preferred_term: cellular response to oxidative stress
    term:
      id: GO:0034599
      label: cellular response to oxidative stress
    modifier: INCREASED
  cell_types:
  - preferred_term: cortical cell of adrenal gland
    term:
      id: CL:0002097
      label: cortical cell of adrenal gland
  downstream:
  - target: Impaired Adrenocortical Cortisol Biosynthesis
    description: >-
      Progressive loss of zona fasciculata cells reduces the functional
      steroidogenic cell mass available to synthesize cortisol.
    evidence:
    - reference: PMID:22634753
      reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "In mice with Nnt loss, higher levels of adrenocortical cell apoptosis and impaired glucocorticoid production were observed."
      explanation: Mouse Nnt-loss model links increased adrenocortical apoptosis directly to impaired glucocorticoid production.
  evidence:
  - reference: PMID:24601690
    reference_title: "Thioredoxin Reductase 2 (TXNRD2) mutation associated with familial glucocorticoid deficiency (FGD)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recently FGD cases caused by mutations in the mitochondrial antioxidant, nicotinamide nucleotide transhydrogenase, have highlighted the importance of redox regulation in steroidogenesis."
    explanation: Frames oxidative-stress-driven adrenocortical failure as a distinct mechanistic class within FGD.
- name: Adrenocortical Replicative Stress and Impaired Steroidogenic Cell Differentiation
  biological_scale: CELLULAR
  description: >-
    MCM4 is part of the MCM2-7 complex, the core replicative helicase required
    for normal DNA replication and genome stability in eukaryotic cells.
    Biallelic loss-of-function MCM4 variants define a third mechanistic route
    to adrenocortical failure, distinct from both ACTH-receptor-signaling
    failure (FGD1-3) and oxidative-stress-driven apoptosis of mature
    steroidogenic cells (FGD4-5): Mcm4-depleted mouse adrenal cortex shows
    grossly abnormal morphology, with non-steroidogenic GATA4- and
    Gli1-positive cells persisting within the cortex and reducing the number
    of cells that differentiate into steroidogenic zona fasciculata cells.
  biological_processes:
  - preferred_term: DNA replication
    term:
      id: GO:0006260
      label: DNA replication
    modifier: LOSS_OF_FUNCTION
  cell_types:
  - preferred_term: cortical cell of adrenal gland
    term:
      id: CL:0002097
      label: cortical cell of adrenal gland
  downstream:
  - target: Impaired Adrenocortical Cortisol Biosynthesis
    description: >-
      Fewer cells differentiate into steroidogenic zona fasciculata cells,
      reducing the functional cortisol-producing cell mass available for
      steroidogenesis.
    evidence:
    - reference: PMID:22354170
      reference_title: "MCM4 mutation causes adrenal failure, short stature, and natural killer cell deficiency in humans."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "histological studies with Mcm4-depleted mice showed grossly abnormal adrenal morphology that was characterized by non-steroidogenic GATA4- and Gli1-positive cells within the steroidogenic cortex, which reduced the number of steroidogenic cells in the zona fasciculata of the adrenal cortex"
      explanation: Mouse model shows the developmental mechanism by which MCM4 loss reduces the number of steroidogenic cells in the zona fasciculata.
  evidence:
  - reference: PMID:22354170
    reference_title: "MCM4 mutation causes adrenal failure, short stature, and natural killer cell deficiency in humans."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Since MCM4 is one part of a MCM2-7 complex recently confirmed as the replicative helicase essential for normal DNA replication and genome stability in all eukaryotes, it is possible that our patients may have an increased risk of neoplastic change."
    explanation: Establishes MCM4's role in the replicative helicase complex, framing the replicative/genomic-stress mechanism as distinct from the receptor and redox routes.
  - reference: PMID:23279877
    reference_title: "Familial glucocorticoid deficiency: New genes and mechanisms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These latest findings expand the spectrum of pathogenetic mechanisms causing adrenal disease and imply that the adrenal may be hypersensitive to replicative and oxidative stresses."
    explanation: Review frames replicative stress (MCM4) alongside oxidative stress (NNT) as the two newly recognized non-receptor mechanistic routes in FGD.
- name: Impaired Adrenocortical Cortisol Biosynthesis
  biological_scale: TISSUE
  description: >-
    Convergent endpoint of both mechanistic routes: whether ACTH signaling
    fails at the receptor (FGD1-3) or redox-competent zona fasciculata cells
    are progressively lost (FGD4-5), net cortisol output from the adrenal
    cortex falls, producing the shared biochemical and clinical phenotype of
    FGD.
  downstream:
  - target: Loss of Cortisol-Mediated Negative Feedback and Compensatory ACTH Hypersecretion
    description: >-
      Failure of cortisol production removes the principal negative-feedback
      signal on the hypothalamic-pituitary-adrenal axis.
    evidence:
    - reference: PMID:19558534
      reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "characterized by elevated plasma ACTH, and low or undetectable cortisol in the absence of overt mineralocorticoid deficiency"
      explanation: Documents the combination of low cortisol and reflexively elevated ACTH that defines the FGD biochemical phenotype.
  - target: Decreased circulating cortisol level
    description: >-
      Impaired cortisol biosynthesis directly produces the low or
      undetectable serum cortisol that is the core biochemical phenotype of
      FGD, unresponsive to exogenous ACTH stimulation.
    evidence:
    - reference: PMID:19558534
      reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "characterized by elevated plasma ACTH, and low or undetectable cortisol in the absence of overt mineralocorticoid deficiency"
      explanation: States low/undetectable cortisol as the direct biochemical consequence of impaired cortisol biosynthesis.
  - target: Hypoglycemia
    description: >-
      Cortisol is required for hepatic gluconeogenesis and counter-regulatory
      glucose defense, so impaired cortisol biosynthesis produces hypoglycemia,
      a presenting and potentially life-threatening feature.
    evidence:
    - reference: PMID:22634753
      reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Patients typically present within the first few months of life with symptoms related to cortisol deficiency including recurrent illnesses/infections, hypoglycaemia, convulsions, failure to thrive and shock."
      explanation: Lists hypoglycemia among the symptoms directly attributed to cortisol deficiency.
  - target: Failure to thrive
    description: >-
      Cortisol deficiency impairs growth and metabolic homeostasis in
      infancy, producing failure to thrive as part of the classic
      presentation.
    evidence:
    - reference: PMID:22634753
      reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Patients typically present within the first few months of life with symptoms related to cortisol deficiency including recurrent illnesses/infections, hypoglycaemia, convulsions, failure to thrive and shock."
      explanation: Lists failure to thrive among the symptoms directly attributed to cortisol deficiency.
  - target: Recurrent or severe infections
    description: >-
      Loss of cortisol's role in immune and metabolic homeostasis increases
      susceptibility to recurrent or overwhelming infection, historically a
      cause of mortality in undiagnosed FGD.
    evidence:
    - reference: PMID:15654338
      reference_title: "Mutations in MRAP, encoding a new interacting partner of the ACTH receptor, cause familial glucocorticoid deficiency type 2."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood."
      explanation: Documents overwhelming infection as a life-threatening consequence of cortisol deficiency.
  evidence:
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
    explanation: Summarizes the convergent biochemical phenotype of impaired cortisol biosynthesis across FGD subtypes.
- name: Preserved Zona Glomerulosa Mineralocorticoid Production
  biological_scale: TISSUE
  description: >-
    The zona glomerulosa (aldosterone-producing layer of the adrenal cortex,
    UBERON:0002053) is regulated principally by the renin-angiotensin-potassium
    axis rather than by ACTH, so it is functionally spared in FGD even when
    the ACTH-dependent zona fasciculata (cortisol-producing layer) fails.
    This is the mechanistic basis for the normal plasma renin activity and
    serum aldosterone that distinguish FGD from combined-deficiency forms of
    primary adrenal insufficiency, such as autoimmune Addison disease,
    congenital adrenal hyperplasia, or classic (complete) STAR-null lipoid
    congenital adrenal hyperplasia, in which mineralocorticoid production is
    also lost.
  evidence:
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
    explanation: States the preserved-mineralocorticoid-production biochemical hallmark that distinguishes FGD from combined adrenal insufficiency.
- name: Loss of Cortisol-Mediated Negative Feedback and Compensatory ACTH Hypersecretion
  biological_scale: ORGANISM
  description: >-
    Absent cortisol negative feedback on the hypothalamus and pituitary
    corticotrophs drives markedly elevated plasma ACTH and other
    proopiomelanocortin (POMC)-derived peptides, including
    melanocyte-stimulating hormone activity, producing the characteristic
    generalized hyperpigmentation of FGD as well as the risk of
    hypoglycemia, failure to thrive, and susceptibility to infection that
    define the untreated clinical course.
  downstream:
  - target: Hyperpigmentation
    description: >-
      Markedly elevated ACTH and other POMC-derived peptides, including
      melanocyte-stimulating hormone activity, act on melanocortin 1
      receptors in melanocytes to produce generalized hyperpigmentation.
    evidence:
    - reference: PMID:19558534
      reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "patients usually present with hypoglycaemia, seizure, jaundice, hyperpigmentation, failure to thrive and frequent or severe infections"
      explanation: Lists hyperpigmentation among the classic presenting features driven by compensatory ACTH hypersecretion.
  - target: Increased circulating ACTH level
    description: >-
      Loss of cortisol-mediated negative feedback on the hypothalamic-pituitary
      axis is the direct cause of the markedly elevated plasma ACTH that
      defines this biochemical phenotype.
    evidence:
    - reference: PMID:19558534
      reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
      explanation: Documents markedly elevated plasma ACTH as the direct readout of lost negative feedback.
  evidence:
  - reference: PMID:15654338
    reference_title: "Mutations in MRAP, encoding a new interacting partner of the ACTH receptor, cause familial glucocorticoid deficiency type 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood."
    explanation: Documents the clinical consequences of unopposed cortisol deficiency if the compensatory HPA response is not corrected by treatment.
  - reference: PMID:22634753
    reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients typically present within the first few months of life with symptoms related to cortisol deficiency including recurrent illnesses/infections, hypoglycaemia, convulsions, failure to thrive and shock."
    explanation: Documents the classic presenting symptom complex of FGD driven by cortisol deficiency.
phenotypes:
- category: Dermatologic
  name: Hyperpigmentation
  description: >-
    Generalized hyperpigmentation of the skin and mucous membranes, resulting
    from markedly elevated ACTH and other POMC-derived peptides acting on
    melanocortin 1 receptors in melanocytes; a cardinal presenting sign.
  phenotype_term:
    preferred_term: Hyperpigmentation of the skin
    term:
      id: HP:0000953
      label: Hyperpigmentation of the skin
  evidence:
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "patients usually present with hypoglycaemia, seizure, jaundice, hyperpigmentation, failure to thrive and frequent or severe infections"
    explanation: Lists hyperpigmentation among the classic presenting features of FGD.
- category: Endocrine
  name: Hypoglycemia
  description: >-
    Cortisol deficiency impairs hepatic gluconeogenesis and counter-regulatory
    glucose defense, causing hypoglycemia that is often the presenting or
    life-threatening feature in infancy.
  phenotype_term:
    preferred_term: Hypoglycemia
    term:
      id: HP:0001943
      label: Hypoglycemia
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:15654338
    reference_title: "Mutations in MRAP, encoding a new interacting partner of the ACTH receptor, cause familial glucocorticoid deficiency type 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood."
    explanation: Identifies hypoglycemia as a major, potentially fatal, consequence of untreated cortisol deficiency in FGD.
- category: Growth
  name: Failure to thrive
  description: >-
    Poor growth and weight gain in infancy, part of the classic FGD
    presentation alongside hypoglycemia and hyperpigmentation.
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  evidence:
  - reference: PMID:22634753
    reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients typically present within the first few months of life with symptoms related to cortisol deficiency including recurrent illnesses/infections, hypoglycaemia, convulsions, failure to thrive and shock."
    explanation: Lists failure to thrive among the classic early-life presenting symptoms of FGD.
- category: Immunologic
  name: Recurrent or severe infections
  description: >-
    Increased susceptibility to recurrent or overwhelming infections in
    infancy and childhood, attributed to loss of cortisol's role in immune
    and metabolic homeostasis; historically a cause of mortality in
    undiagnosed FGD.
  phenotype_term:
    preferred_term: Recurrent infections
    term:
      id: HP:0002719
      label: Recurrent infections
  evidence:
  - reference: PMID:15654338
    reference_title: "Mutations in MRAP, encoding a new interacting partner of the ACTH receptor, cause familial glucocorticoid deficiency type 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood."
    explanation: Documents overwhelming infection as a life-threatening consequence of untreated FGD.
- category: Endocrine
  name: Increased circulating ACTH level
  description: >-
    Markedly elevated plasma ACTH reflects loss of cortisol-mediated negative
    feedback on the hypothalamic-pituitary axis; together with low cortisol,
    this is the diagnostic biochemical signature of FGD.
  phenotype_term:
    preferred_term: Increased circulating ACTH level
    term:
      id: HP:0003154
      label: Increased circulating ACTH level
  evidence:
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
    explanation: Establishes elevated ACTH with low cortisol as the core biochemical phenotype.
- category: Endocrine
  name: Decreased circulating cortisol level
  description: >-
    Low or undetectable serum cortisol, unresponsive to exogenous ACTH
    (cosyntropin) stimulation, in the absence of overt mineralocorticoid
    deficiency.
  phenotype_term:
    preferred_term: Decreased circulating cortisol level
    term:
      id: HP:0008163
      label: Decreased circulating cortisol level
  evidence:
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characterized by elevated plasma ACTH, and low or undetectable cortisol in the absence of overt mineralocorticoid deficiency"
    explanation: Documents low/undetectable cortisol with preserved mineralocorticoid status as the defining biochemical phenotype.
- category: Growth
  name: Tall stature
  subtype: FGD1
  description: >-
    Unusually tall stature and excessive linear growth, with increased head
    circumference, described specifically in FGD type 1 (MC2R-related) but
    not FGD type 2 (MRAP-related); growth hormone and IGF-I levels are
    normal, and growth normalizes toward the population mean after
    glucocorticoid replacement is started.
  phenotype_term:
    preferred_term: Tall stature
    term:
      id: HP:0000098
      label: Tall stature
  evidence:
  - reference: PMID:11012566
    reference_title: "Tall stature in familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients demonstrated excessive linear growth over that predicted from parental indices and increased head circumference."
    explanation: Documents excessive linear growth and macrocephaly in FGD patients (predominantly MC2R-mutation-positive) prior to treatment.
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Tall stature is associated with mutations in MC2R but not in MRAP."
    explanation: Establishes that tall stature specifically distinguishes FGD1 (MC2R) from FGD2 (MRAP).
biochemical:
- name: Serum Cortisol
  presence: Decreased
  context: >-
    Low or undetectable basal serum cortisol, unresponsive to cosyntropin
    (synthetic ACTH) stimulation, reflecting the shared endocrine endpoint of
    all FGD subtypes.
  evidence:
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characterized by elevated plasma ACTH, and low or undetectable cortisol in the absence of overt mineralocorticoid deficiency"
    explanation: Documents low/undetectable cortisol as a core biochemical finding of FGD.
- name: Plasma ACTH
  presence: Increased
  context: >-
    Markedly elevated plasma ACTH from loss of cortisol-mediated negative
    feedback; median plasma ACTH at presentation is similarly elevated in
    both FGD1 and FGD2 (1409 and 1250 ng/l respectively in one cohort).
  evidence:
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
    explanation: Establishes markedly elevated plasma ACTH as a defining biochemical finding of FGD.
- name: Plasma Renin Activity
  presence: Normal
  context: >-
    Preserved (not elevated) plasma renin activity is a key discriminating
    feature of FGD versus combined glucocorticoid-and-mineralocorticoid forms
    of primary adrenal insufficiency, in which renin is compensatorily
    elevated. Reflects intact renin-angiotensin-dependent regulation of the
    zona glomerulosa despite ACTH-dependent zona fasciculata failure.
  evidence:
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
    explanation: States the preserved mineralocorticoid axis (renin/aldosterone) that distinguishes FGD from combined-deficiency primary adrenal insufficiency.
  readouts:
  - target: Preserved Zona Glomerulosa Mineralocorticoid Production
    relationship: READOUT_OF
    interpretation: >-
      Normal (non-elevated) renin distinguishes isolated FGD from
      combined-deficiency primary adrenal insufficiency, in which renin rises
      compensatorily.
    evidence:
    - reference: PMID:19558534
      reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "characterized by elevated plasma ACTH, and low or undetectable cortisol in the absence of overt mineralocorticoid deficiency"
      explanation: Supports the absence of overt mineralocorticoid deficiency, of which renin is the primary regulator and biochemical readout.
- name: Serum Aldosterone
  presence: Normal
  context: >-
    Preserved (not decreased) serum aldosterone, the other half of the
    mineralocorticoid-sparing biochemical signature that discriminates FGD
    from combined-deficiency primary adrenal insufficiency.
  evidence:
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
    explanation: Documents preserved mineralocorticoid (aldosterone) production as characteristic of FGD.
  readouts:
  - target: Preserved Zona Glomerulosa Mineralocorticoid Production
    relationship: READOUT_OF
    interpretation: >-
      Normal (non-decreased) aldosterone distinguishes isolated FGD from
      combined-deficiency primary adrenal insufficiency.
    evidence:
    - reference: PMID:19558534
      reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The biochemical findings are a markedly elevated plasma ACTH in the presence of low cortisol but with a preserved mineralocorticoid production and are characteristic of ACTH insensitivity."
      explanation: Directly states preserved mineralocorticoid (aldosterone) production.
animal_models:
- name: Nnt-loss mouse
  species: Mouse
  genotype: Nnt loss-of-function (C57BL/6J-background Nnt-deficient line)
  description: >-
    Mice lacking functional Nnt were used to test whether loss of this
    NADPH-generating antioxidant enzyme reproduces the oxidative-stress route
    to adrenocortical failure identified in human FGD4 (NNT-related FGD).
  publication: PMID:22634753
  modeled_mechanisms:
  - target: Adrenocortical Oxidative Stress and Apoptosis
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Nnt-loss mice show increased adrenocortical cell apoptosis and impaired
      glucocorticoid production, recapitulating the oxidative-stress-driven
      cell-loss mechanism proposed for human NNT-related FGD (FGD4).
    limitations: >-
      The widely used C57BL/6J substrain carries a spontaneous Nnt deletion,
      so mouse adrenal zonation, steroidogenic regulation, and lifespan differ
      from human; the mouse data establish increased apoptosis and reduced
      glucocorticoid output but do not by themselves reproduce the full human
      FGD4 phenotype (e.g., the specific hyperpigmentation/ACTH-resistance
      presentation).
    readouts:
    - name: Adrenocortical cell apoptosis
      target: Adrenocortical Oxidative Stress and Apoptosis
      direction: INCREASED
      interpretation: >-
        Increased apoptosis in Nnt-deficient mouse adrenal cortex supports
        oxidative stress as the driver of zona fasciculata cell loss in this
        mechanistic route.
      evidence:
      - reference: PMID:22634753
        reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "In mice with Nnt loss, higher levels of adrenocortical cell apoptosis and impaired glucocorticoid production were observed."
        explanation: Reports the apoptosis and glucocorticoid-output measurements behind this readout.
    evidence:
    - reference: PMID:22634753
      reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "In mice with Nnt loss, higher levels of adrenocortical cell apoptosis and impaired glucocorticoid production were observed."
      explanation: Supports treating the Nnt-loss mouse as informative for the oxidative-stress-driven adrenocortical failure node.
experimental_models:
- name: NNT-knockdown human adrenocortical cell line
  description: >-
    Human adrenocortical cell line with NNT knocked down, used to test
    whether loss of NNT directly impairs mitochondrial redox homeostasis.
  experimental_model_type: CELL_LINE
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_types:
  - preferred_term: cortical cell of adrenal gland
    term:
      id: CL:0002097
      label: cortical cell of adrenal gland
  publication: PMID:22634753
  modeled_mechanisms:
  - target: Adrenocortical Mitochondrial Antioxidant Defense Failure
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      NNT knockdown reproduces the redox-impairment step of the NNT-related
      mechanism directly in a human adrenocortical cell background.
    limitations: >-
      A cultured, likely immortalized/carcinoma-derived adrenocortical cell
      line lacks intact HPA-axis regulation, normal adrenal architecture, and
      the in vivo cellular turnover relevant to the chronic human disease
      course.
    readouts:
    - name: Redox potential and reactive oxygen species levels
      target: Adrenocortical Mitochondrial Antioxidant Defense Failure
      direction: INCREASED
      interpretation: >-
        Increased ROS and impaired redox potential after NNT knockdown
        directly demonstrate the proposed biochemical mechanism of NNT-related
        adrenocortical failure.
      evidence:
      - reference: PMID:22634753
        reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "NNT knockdown in a human adrenocortical cell line resulted in impaired redox potential and increased reactive oxygen species (ROS) levels."
        explanation: Reports the redox potential and ROS measurements behind this readout.
    evidence:
    - reference: PMID:22634753
      reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "NNT knockdown in a human adrenocortical cell line resulted in impaired redox potential and increased reactive oxygen species (ROS) levels."
      explanation: Supports treating the NNT-knockdown cell line as informative for the antioxidant-defense-failure node.
- name: TXNRD2-deficient human adrenocortical cell line
  description: >-
    Human adrenocortical cell line with TXNRD2 deficiency, used to test
    whether loss of TXNRD2 directly impairs mitochondrial redox homeostasis,
    paralleling the NNT-knockdown system.
  experimental_model_type: CELL_LINE
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_types:
  - preferred_term: cortical cell of adrenal gland
    term:
      id: CL:0002097
      label: cortical cell of adrenal gland
  publication: PMID:24601690
  modeled_mechanisms:
  - target: Adrenocortical Mitochondrial Antioxidant Defense Failure
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      TXNRD2 deficiency reproduces the redox-impairment step of the
      thioredoxin-dependent arm of the antioxidant-defense mechanism directly
      in a human adrenocortical cell background.
    limitations: >-
      A cultured, likely immortalized/carcinoma-derived adrenocortical cell
      line lacks intact HPA-axis regulation, normal adrenal architecture, and
      the in vivo cellular turnover relevant to the chronic human disease
      course.
    readouts:
    - name: Redox homeostasis
      target: Adrenocortical Mitochondrial Antioxidant Defense Failure
      direction: ALTERED
      interpretation: >-
        Impaired redox homeostasis after TXNRD2 loss directly demonstrates the
        proposed biochemical mechanism of TXNRD2-related adrenocortical
        failure, mechanistically paralleling NNT loss.
      evidence:
      - reference: PMID:24601690
        reference_title: "Thioredoxin Reductase 2 (TXNRD2) mutation associated with familial glucocorticoid deficiency (FGD)."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "TXNRD2 deficiency leads to impaired redox homeostasis in a human adrenocortical cell line."
        explanation: Reports the redox homeostasis measurement behind this readout.
    evidence:
    - reference: PMID:24601690
      reference_title: "Thioredoxin Reductase 2 (TXNRD2) mutation associated with familial glucocorticoid deficiency (FGD)."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "TXNRD2 deficiency leads to impaired redox homeostasis in a human adrenocortical cell line."
      explanation: Supports treating the TXNRD2-deficient cell line as informative for the antioxidant-defense-failure node.
differential_diagnoses:
- name: Triple A (Allgrove) Syndrome
  description: >-
    The classic clinical differential for FGD: also presents with ACTH-resistant
    primary adrenal insufficiency and preserved mineralocorticoid production,
    caused by biallelic AAAS variants (a nuclear pore complex protein), but is
    distinguished by the additional cardinal features of esophageal achalasia
    and alacrima, plus progressive neurological involvement not seen in
    isolated FGD.
  distinguishing_features:
  - Esophageal achalasia is a defining feature of Triple A syndrome, absent in FGD.
  - Alacrima (deficient tear production) is a defining feature of Triple A syndrome, absent in FGD.
  - Progressive peripheral/central neuropathy or cerebellar ataxia occur in Triple A syndrome but not isolated FGD.
  - AAAS sequencing distinguishes the two when the clinical triad of Triple A syndrome is incomplete.
  evidence:
  - reference: PMID:22634753
    reference_title: "Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of particular relevance to our patients is Triple A syndrome (OMIM 231550)"
    explanation: The NNT/FGD4 discovery paper explicitly identifies Triple A syndrome as the closest relevant differential, sharing an oxidative-stress mechanistic theme.
- name: Autoimmune Addison Disease and Other Combined-Deficiency Causes of Chronic Primary Adrenal Insufficiency
  description: >-
    Autoimmune Addison disease and other causes of combined-deficiency
    chronic primary adrenal insufficiency (e.g., adrenoleukodystrophy, adrenal
    hemorrhage, infiltrative or infectious adrenalitis) present with cortisol
    deficiency and hyperpigmentation similarly to FGD, but additionally lose
    zona glomerulosa (aldosterone) function, producing hyponatremia,
    hyperkalemia, salt-wasting, and compensatory hyperreninemia that are
    absent in FGD. FGD itself sits within the broader chronic primary adrenal
    insufficiency umbrella (see `parents`) as its isolated-glucocorticoid,
    genetic-only branch; this differential names the combined-deficiency
    causes within that same umbrella that must be excluded, of which
    autoimmune Addison disease (`kb/disorders/Addisons_Disease.yaml`) is the
    most common.
  disease_term:
    preferred_term: autoimmune primary adrenal insufficiency
    term:
      id: MONDO:0100480
      label: autoimmune primary adrenal insufficiency
  distinguishing_features:
  - Elevated plasma renin activity (compensatory hyperreninemia) occurs in combined-deficiency primary adrenal insufficiency but not FGD.
  - Decreased aldosterone (mineralocorticoid deficiency) occurs in combined-deficiency primary adrenal insufficiency but not FGD.
  - Hyponatremia, hyperkalemia, and salt-wasting occur in combined-deficiency primary adrenal insufficiency but not FGD.
  evidence:
  - reference: PMID:19558534
    reference_title: "Phenotypic characteristics of familial glucocorticoid deficiency (FGD) type 1 and 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characterized by elevated plasma ACTH, and low or undetectable cortisol in the absence of overt mineralocorticoid deficiency"
    explanation: States the preserved-mineralocorticoid criterion used to exclude combined-deficiency primary adrenal insufficiency in the FGD diagnostic cohort.
- name: Classic (STAR-Null) Lipoid Congenital Adrenal Hyperplasia
  description: >-
    Complete loss-of-function STAR mutations cause a severe, distinct
    disorder with combined adrenal and gonadal steroidogenic failure
    (glucocorticoid, mineralocorticoid, and sex steroid deficiency) and
    disordered sex development in 46,XY individuals, in contrast to the
    partial-function STAR mutations underlying FGD3, which spare
    mineralocorticoid and gonadal steroidogenesis.
  distinguishing_features:
  - Combined mineralocorticoid deficiency (salt-wasting) occurs in classic lipoid congenital adrenal hyperplasia but not FGD3.
  - Disordered sex development in 46,XY individuals occurs in classic lipoid congenital adrenal hyperplasia but not FGD3.
  evidence:
  - reference: PMID:19773404
    reference_title: "Nonclassic lipoid congenital adrenal hyperplasia masquerading as familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in STAR usually cause lipoid congenital adrenal hyperplasia, a disorder characterized by both gonadal and adrenal steroid deficiency. Our results demonstrate that certain mutations in STAR (R192C and the previously reported R188C) can present with a phenotype indistinguishable from that seen in FGD."
    explanation: Directly contrasts the combined-deficiency phenotype of classic STAR loss with the FGD-like phenotype of partial-function STAR mutations.
treatments:
- name: Hydrocortisone Replacement Therapy
  description: >-
    Lifelong glucocorticoid replacement (typically hydrocortisone in
    children) corrects cortisol deficiency and is the mainstay of FGD
    treatment; unlike combined-deficiency primary adrenal insufficiency,
    mineralocorticoid replacement is not required because zona glomerulosa
    function is preserved. Adequate replacement also normalizes the
    excessive linear growth characteristic of untreated FGD type 1.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: cortisol
      term:
        id: CHEBI:17650
        label: cortisol
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: Impaired Adrenocortical Cortisol Biosynthesis
    treatment_effect: RESTORES
    description: >-
      Exogenous hydrocortisone substitutes directly for the deficient
      endogenous cortisol, regardless of which upstream route (receptor
      signaling failure, oxidative or replicative adrenocortical stress)
      caused the biosynthetic failure.
    evidence:
    - reference: PMID:15654338
      reference_title: "Mutations in MRAP, encoding a new interacting partner of the ACTH receptor, cause familial glucocorticoid deficiency type 2."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood."
      explanation: Establishes the life-saving necessity of glucocorticoid replacement in correcting the cortisol deficiency.
  - target: Loss of Cortisol-Mediated Negative Feedback and Compensatory ACTH Hypersecretion
    treatment_effect: INHIBITS
    description: >-
      Restoring circulating cortisol reinstates negative feedback on the
      hypothalamic-pituitary-adrenal axis, suppressing the compensatory ACTH
      hypersecretion and reversing the excessive linear growth it drives in
      FGD type 1.
    evidence:
    - reference: PMID:11012566
      reference_title: "Tall stature in familial glucocorticoid deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Growth charts suggest that the excessive growth is reduced to normal following the introduction of glucocorticoid replacement."
      explanation: Demonstrates that glucocorticoid replacement reverses the ACTH-driven excessive growth of FGD type 1, evidencing suppression of the upstream hypersecretion.
  evidence:
  - reference: PMID:11012566
    reference_title: "Tall stature in familial glucocorticoid deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Growth charts suggest that the excessive growth is reduced to normal following the introduction of glucocorticoid replacement."
    explanation: Demonstrates the clinical benefit of glucocorticoid replacement in normalizing the excessive growth of FGD type 1.
  - reference: PMID:15654338
    reference_title: "Mutations in MRAP, encoding a new interacting partner of the ACTH receptor, cause familial glucocorticoid deficiency type 2."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals are deficient in cortisol and, if untreated, are likely to succumb to hypoglycemia or overwhelming infection in infancy or childhood."
    explanation: Establishes the life-saving necessity of glucocorticoid replacement in FGD.
📚

References & Deep Research

Deep Research

1
Falcon ▸
Familial Glucocorticoid Deficiency: Disease Characteristics Research Report
Edison Scientific Literature 34 citations 2026-08-26T18:01:48.346937

Familial Glucocorticoid Deficiency: Disease Characteristics Research Report

Executive summary

Familial glucocorticoid deficiency (FGD) is a rare, usually autosomal-recessive form of primary adrenal insufficiency characterized by deficient cortisol production despite markedly elevated adrenocorticotropic hormone (ACTH). In its classic form, mineralocorticoid secretion is preserved. The central clinical risks are hypoglycemia, seizures or hypoglycemic brain injury, infection-associated adrenal crisis, shock, and death if treatment is delayed. Hyperpigmentation is the most recognizable chronic sign.

The narrow, classical definition comprises FGD type 1 due to biallelic MC2R variants and FGD type 2 due to biallelic MRAP variants. Contemporary usage is broader and may include FGD-like disease caused by NNT, TXNRD2, and partial defects of STAR or CYP11A1. MCM4-associated syndromic adrenal insufficiency and AAAS-related Triple A syndrome are important phenocopies rather than uncomplicated isolated FGD. A 62-patient comparison found median presentation at 2.0 years for MC2R-FGD versus 0.08 years for MRAP-FGD. Recent research has particularly expanded recognition of mitochondrial redox disease: a 2023 human report linked NNT deficiency to progressive, irreversible germ-cell loss and emphasized fertility surveillance. No FGD-specific gene, RNA, or cell therapy—and no disease-specific interventional trial—was identified.

Evidence scope. Most evidence is aggregated disease-level evidence from cohorts, case series, and reviews, not individual EHR data. The strongest quantitative sources retrieved were a 62-person FGD1/FGD2 cohort, a 95-child Turkish PAI cohort, and a 155-person UK pediatric PAI cohort. Because the latter two include non-FGD genetic adrenal disorders, their percentages must not be interpreted as population prevalence of FGD.

1. Disease information

Definition and classification

FGD is an inherited ACTH-resistance disorder in which adrenal cortisol synthesis is inadequate despite high ACTH. Classic biochemical disease consists of low or undetectable cortisol, very high ACTH, and absent overt mineralocorticoid deficiency. The defining distinction from generalized primary adrenal failure is therefore the relative preservation of the zona glomerulosa/renin–angiotensin–aldosterone axis. Partial STAR and CYP11A1 deficiencies may violate this simple distinction by also causing salt loss. (chung2010phenotypiccharacteristicsof pages 1-2, malikova2014novelinsightinto pages 7-8, guran2016rarecausesof pages 4-6)

A concise source statement is: “Familial glucocorticoid deficiency is a rare autosomal recessive disorder characterized by isolated glucocorticoid deficiency due to ACTH resistance.” This is a close rendering of the 2010 cohort abstract rather than a verbatim quotation longer than necessary. (chung2010phenotypiccharacteristicsof pages 1-2)

Identifiers and synonyms

The following identifiers are suitable starting annotations but should be verified against the current release of each ontology before database ingestion:

  • Preferred label: familial glucocorticoid deficiency.
  • Common synonyms: FGD; hereditary adrenocortical unresponsiveness to ACTH; hereditary unresponsiveness to adrenocorticotropic hormone; familial ACTH resistance syndrome; glucocorticoid deficiency with normal mineralocorticoid activity.
  • OMIM: FGD type 1/MC2R is commonly represented as OMIM phenotype 202200; FGD type 2/MRAP has a separate phenotype record. Exact current subtype record mappings should be verified directly in OMIM.
  • Orphanet: commonly indexed under ORPHA:361; verify current hierarchy and subtype mappings.
  • MONDO: a dedicated FGD concept is expected, but a stable MONDO identifier was not established from the retrieved primary literature; do not populate an unverified ID.
  • ICD-10-CM: no reliably specific FGD code was identified. It is usually coded under primary adrenocortical insufficiency/other specified adrenocortical insufficiency rather than Addison autoimmune disease.
  • ICD-11, MeSH, SNOMED CT: use the most specific current primary adrenal insufficiency/ACTH-resistance concept available; release-specific identifiers require direct terminology lookup.

These terminology statements are resource-level annotations, whereas the clinical and genetic claims below come from aggregated research cohorts.

2. Etiology

Causal factors

FGD is principally monogenic and germline, not infectious, toxic, lifestyle-associated, or autoimmune. Biallelic loss-of-function variants impair one of three major biological modules:

  1. ACTH reception: MC2R or its accessory/trafficking protein MRAP.
  2. Mitochondrial antioxidant defense: NNT and TXNRD2.
  3. Early steroidogenesis: partial STAR or CYP11A1 deficiency.

Additional syndromic disorders can generate an FGD-like phenotype, including MCM4 deficiency; AAAS-related Triple A syndrome causes ACTH-resistant adrenal insufficiency but should be separately classified when alacrima, achalasia, or neurologic disease is present. (malikova2014novelinsightinto pages 7-8, refaei2018familialglucocorticoiddeficiency pages 2-2, malikova2014novelinsightinto pages 11-12)

Genetic risk

Risk is conferred by pathogenic or likely pathogenic variants on both alleles. Consanguinity and founder ancestry increase the probability of homozygosity. In the Turkish cohort, 80% of genetically diagnosed children were homozygous; among CYP11A1 cases, 8/9 were consanguineous. Regional recurrent variants included MC2R c.560delT, CYP11A1 p.Arg451Trp, and an MRAP splice-region deletion. (guran2016rarecausesof pages 6-7, guran2016rarecausesof pages 4-4, guran2016rarecausesof pages 4-6)

The UK cohort identified an ancestry-associated MC2R p.Ser74Ile founder variant in 20/30 MC2R cases, particularly among people of Irish or Scottish ancestry. These are diagnostic-enrichment observations, not population penetrance estimates. (buonocore2021geneticanalysisof pages 5-6, buonocore2021geneticanalysisof pages 11-12)

Environmental, protective, and gene–environment factors

No environmental exposure is known to cause inherited FGD, and no validated protective allele, diet, exercise pattern, toxin avoidance strategy, or vaccine prevents the genotype. Environmental stressors nevertheless strongly modify clinical expression: fasting, vomiting, fever, trauma, surgery, and severe infection raise cortisol demand and may precipitate hypoglycemia or adrenal crisis. Thus, the clinically important gene–environment interaction is fixed impaired cortisol reserve × acute physiological stress. Early diagnosis, reliable hormone access, avoidance of prolonged fasting, and stress dosing are protective against manifestations, not against inheritance. Severe infections are repeatedly described among presenting features. (malikova2014novelinsightinto pages 7-8, refaei2018familialglucocorticoiddeficiency pages 2-2)

3. Phenotypes

Phenotype Type, timing, course, and frequency Suggested HPO term
Hyperpigmentation Clinical sign caused by chronic ACTH/POMC peptide excess; often progressive and generalized. Common/characteristic, but no defensible pooled percentage was retrieved. Improves after adequate replacement. Hyperpigmentation of the skin — HP:0000953
Hypoglycemia Laboratory abnormality and acute manifestation, commonly neonatal or pediatric; episodic during fasting or illness and potentially severe. Hypoglycemia — HP:0001943
Seizures Acute neurologic sign, usually secondary to severe hypoglycemia; may produce lasting neurologic morbidity. Seizure — HP:0001250
Low cortisol Core laboratory abnormality; persistent without replacement and with low/attenuated cosyntropin response. Decreased circulating cortisol level — HP:0008163
Elevated ACTH Core laboratory abnormality reflecting loss of cortisol feedback and/or adrenal ACTH resistance. Increased circulating ACTH level — HP term should be release-verified
Failure to thrive/poor weight gain Pediatric sign; variable, chronic before diagnosis, and generally improves with treatment. Failure to thrive — HP:0001508
Fatigue/weakness Symptom of cortisol deficiency; nonspecific and variable. Fatigue — HP:0012378; Muscle weakness — HP:0001324
Adrenal crisis, shock Acute life-threatening complication during illness, vomiting, fasting, trauma, or missed treatment. Adrenal crisis / hypotension / shock — verify current specific HPO concepts
Tall stature/accelerated linear growth Particularly associated with untreated MC2R-FGD1; glucocorticoid treatment normalizes growth rate. Tall stature — HP:0000098; Accelerated linear growth — release-verify
Normal electrolytes and preserved aldosterone Important negative/biochemical characteristic in classic FGD; not an HPO abnormality. Salt wasting suggests broader steroidogenic disease or evolving mineralocorticoid impairment. No disease phenotype term required
Gonadal dysfunction in NNT deficiency Extra-adrenal, progressive phenotype: hypergonadotropic hypogonadism, testicular atrophy/TART, azoospermia, and germ-cell loss may emerge after puberty. Male infertility — HP:0003251; Azoospermia — HP:0000027; Hypergonadotropic hypogonadism — HP:0000817

Age and genotype–phenotype data

In the 62-patient study, 40 patients had MC2R variants and 22 had MRAP variants. FGD1 presented at median age 2.0 years (range 0.02–16), compared with 0.08 years (birth–1.6 years) for FGD2. Mean/summary height SDS was +1.75 in FGD1 versus +0.12 in FGD2. The proposed explanation is that MC2R missense alleles frequently preserve partial activity, whereas MRAP nonsense or splice variants may abolish accessory-protein function. (chung2010phenotypiccharacteristicsof pages 1-2)

The same study linked FGD1 tall stature to prolonged ACTH excess and cortisol deficiency; glucocorticoid replacement normalized growth velocity. This is a genotype-associated clue, not a universal phenotype. (chung2010phenotypiccharacteristicsof pages 4-5)

Quality of life

No FGD-specific EQ-5D, SF-36, PROMIS, or validated disease-specific quality-of-life dataset was retrieved. Expected burden includes lifelong multidose medication, fear of adrenal crisis, emergency planning, disrupted school/work during illness, neurologic disability after severe hypoglycemia, and—in NNT disease—fertility concerns. These impacts are clinically credible but have not been quantified specifically for FGD in the retrieved evidence.

4. Genetic and molecular information

The principal gene–phenotype evidence is summarized below.

Gene or subtype Core molecular defect Typical clinical clues / extra-adrenal features Key quantitative evidence
MC2R / FGD type 1 ACTH receptor defect causing adrenal ACTH resistance; many variants are missense with residual receptor function (chung2010phenotypiccharacteristicsof pages 1-2, chung2010phenotypiccharacteristicsof pages 4-5) Isolated glucocorticoid deficiency with high ACTH, low/undetectable cortisol, usually preserved mineralocorticoid function; hyperpigmentation, hypoglycemia/seizures; later presentation and tall stature are characteristic clues (chung2010phenotypiccharacteristicsof pages 1-2, chung2010phenotypiccharacteristicsof pages 4-5) In the 62-patient FGD cohort, 40/62 had MC2R variants; type 1 accounted for ~25% of all FGD, with median presentation age 2.0 y (range 0.02–16) and height SDS +1.75 (chung2010phenotypiccharacteristicsof pages 1-2). In the UK pediatric PAI cohort, MC2R was 30/155 (19.4%); p.S74I occurred in 20/30 cases, consistent with an Irish/Scottish founder effect (buonocore2021geneticanalysisof pages 5-6, buonocore2021geneticanalysisof pages 1-2).
MRAP / FGD type 2 Defect of melanocortin 2 receptor accessory protein, impairing MC2R trafficking/function; variants often abolish protein (nonsense/splice) (chung2010phenotypiccharacteristicsof pages 1-2) Similar biochemical picture to FGD1, but typically earlier neonatal/infant presentation; not associated with the tall-stature tendency seen in FGD1 (chung2010phenotypiccharacteristicsof pages 1-2, refaei2018familialglucocorticoiddeficiency pages 1-2) In the 62-patient FGD cohort, 22/62 had MRAP variants; type 2 accounted for ~20% of all FGD, with median presentation age 0.08 y (birth to 1.6 y) and height SDS +0.12 (chung2010phenotypiccharacteristicsof pages 1-2). In the Turkish nationwide pediatric PAI cohort, MRAP variants were found in 9/95 children; recurrent c.IVS3ds±1delG suggested a regional founder effect (guran2016rarecausesof pages 1-2, guran2016rarecausesof pages 4-6).
NNT Mitochondrial inner-membrane defect impairing NADPH generation and antioxidant defense, increasing ROS-mediated cellular injury (malikova2014novelinsightinto pages 7-8, ferreux2023testicularimpairmentin pages 1-2, ferreux2023testicularimpairmentin pages 6-7) Primary adrenal insufficiency/FGD-like disease; extra-adrenal clues can include progressive gonadal dysfunction. Reported manifestations include testicular adrenal rest tumor, Sertoli cell-only syndrome, hypergonadotropic hypogonadism, and azoospermia (ferreux2023testicularimpairmentin pages 1-2, ferreux2023testicularimpairmentin pages 6-7) NNT variants were found in 7/95 children in the Turkish cohort and 6.5% of the UK pediatric PAI cohort (guran2016rarecausesof pages 1-2, buonocore2021geneticanalysisof pages 2-3, buonocore2021geneticanalysisof pages 1-2). UK data note presentation usually between 6 months and 4 years (buonocore2021geneticanalysisof pages 11-12). A 2023 case described a 35-year-old man whose intensified glucocorticoids for 8 months did not improve TART volume or sperm production (ferreux2023testicularimpairmentin pages 1-2).
TXNRD2 Mitochondrial thioredoxin reductase defect affecting redox homeostasis/ROS detoxification, mechanistically related to NNT-dependent antioxidant pathways (malikova2014novelinsightinto pages 11-12) FGD-like/PAI presentation is reported, but specific phenotype details were limited in the gathered evidence; consider potential extra-adrenal oxidative-stress vulnerability (malikova2014novelinsightinto pages 11-12) In the UK pediatric PAI cohort, TXNRD2 accounted for 4.5% of genetically solved cases overall (7/155) (buonocore2021geneticanalysisof pages 1-2). The gathered evidence supports mechanism and cohort frequency, but detailed FGD-specific clinical quantitation was not retrieved (malikova2014novelinsightinto pages 11-12, buonocore2021geneticanalysisof pages 1-2).
Partial STAR / partial CYP11A1 deficiency Partial loss of early steroidogenesis steps can mimic isolated glucocorticoid deficiency; CYP11A1 can be disrupted by missplicing, including variants initially predicted benign/synonymous (maharaj2019predictedbenignand pages 3-3, guran2016rarecausesof pages 4-6, buonocore2021geneticanalysisof pages 11-12) Can present as FGD-like pediatric adrenal insufficiency; clinical clue in UK cohort was childhood ketotic hypoglycemia; some cases require mineralocorticoid replacement or show genital findings, so these are not always purely isolated FGD (guran2016rarecausesof pages 1-2, guran2016rarecausesof pages 4-6, buonocore2021geneticanalysisof pages 11-12) In the Turkish cohort, CYP11A1 variants occurred in 9/95 children, all 9 carrying recurrent p.R451W from 8 unrelated families; 6/9 (66%) had salt-wasting and 8/9 (89%) had consanguinity (guran2016rarecausesof pages 4-4, guran2016rarecausesof pages 4-6). In the UK cohort, CYP11A1 accounted for 7.7% and STAR for 3.9% of 155 cases (buonocore2021geneticanalysisof pages 1-2).
MCM4 DNA replication/repair-related defect associated with adrenal insufficiency rather than classic ACTH-receptor pathway failure (malikova2014novelinsightinto pages 7-8) Important syndromic clue set includes growth retardation and natural killer cell deficiency; not classic isolated FGD, but may enter the differential in childhood adrenal insufficiency (buonocore2021geneticanalysisof pages 11-12) Gathered evidence identifies MCM4 as reported in an Irish travelling community and as a cause of progressive PAI (malikova2014novelinsightinto pages 7-8). No robust frequency figures specific to MCM4 were retrieved in the gathered FGD-focused evidence.
AAAS (Triple A syndrome) — differential / phenocopy Nuclear pore protein defect (ALADIN), causing ACTH-insensitive adrenal insufficiency but typically syndromic, not classic isolated FGD (buonocore2021geneticanalysisof pages 1-2) Key differentiating clues are alacrima and achalasia, often with neurologic features; useful differential when ACTH-resistant adrenal insufficiency is suspected (refaei2018familialglucocorticoiddeficiency pages 2-2) In the UK pediatric PAI cohort, AAAS accounted for 7.1% (11/155) of genetically diagnosed cases (buonocore2021geneticanalysisof pages 1-2). Case-based differential guidance emphasizes excluding Triple A when alacrima/achalasia are present (refaei2018familialglucocorticoiddeficiency pages 2-2).

Table: This table summarizes the main familial glucocorticoid deficiency genes and closely related differentials, highlighting mechanism, clinical clues, and quantitative cohort evidence. It is useful for linking genotype to phenotype and for prioritizing diagnostic testing.

Gene and variant interpretation

  • MC2R: biallelic variants cause FGD1. Many are missense changes that impair ligand binding, signal transduction, folding, or surface expression. Approximately 40 distinct missense changes had been reported in the nationwide-cohort discussion. (guran2016rarecausesof pages 6-7)
  • MRAP: biallelic nonsense, frameshift, or splice variants cause FGD2 by preventing normal MC2R trafficking and signaling. More complete functional loss explains, at least partly, earlier presentation. (chung2010phenotypiccharacteristicsof pages 1-2)
  • NNT: recessive variants reduce mitochondrial NADPH generation and antioxidant capacity. NNT variants represented 6.5% of the 155-person UK unresolved-PAI cohort and seven patients in the Turkish cohort. (guran2016rarecausesof pages 1-2, buonocore2021geneticanalysisof pages 2-3, buonocore2021geneticanalysisof pages 1-2)
  • TXNRD2: biallelic mitochondrial thioredoxin-reductase defects cause an oxidative-stress FGD phenotype; TXNRD2 accounted for 4.5% of the UK cohort. (malikova2014novelinsightinto pages 11-12, buonocore2021geneticanalysisof pages 1-2)
  • STAR/CYP11A1: partial loss can preserve enough fetal gonadal steroidogenesis to avoid classic lipoid congenital adrenal hyperplasia while presenting later with an FGD-like picture. CYP11A1 p.Arg451Trp occurred in nine Turkish patients from eight families; six of nine had salt wasting, showing why these patients should not automatically be labeled as having strictly isolated FGD. (guran2016rarecausesof pages 4-4, guran2016rarecausesof pages 4-6)
  • CYP11A1 missplicing: functional study showed that variants predicted benign or synonymous can disrupt RNA splicing. Therefore, apparently innocuous exonic variants require RNA/minigene assessment when phenotype and segregation support causality. (maharaj2019predictedbenignand pages 3-3)

The Turkish study found 43 deleterious variants: 24 missense, 7 nonsense, 5 frameshift, 3 in-frame deletion, 2 splice-site, and 2 whole-gene/exon deletions; 22/43 (51%) were previously unreported. These figures describe a mixed pediatric PAI cohort, not FGD alone. (guran2016rarecausesof pages 4-4)

Variant curation recommendations

All disease-causing variants are expected to be germline. Classification should follow ACMG/AMP criteria using segregation, rarity in ancestry-matched gnomAD data, predicted consequence, functional assays, and phenotype specificity. Exact gnomAD/TOPMed allele frequencies and ClinVar classifications must be retrieved variant by variant; cohort papers cannot substitute for current database records. Missense, nonsense, frameshift, splice, exon/gene deletion, and in-frame deletion classes are all documented. RNA evidence is especially important for CYP11A1. (guran2016rarecausesof pages 4-4, maharaj2019predictedbenignand pages 3-3)

Modifiers, epigenetics, and chromosomal abnormalities

No validated modifier gene, protective allele, FGD-specific methylation signature, histone alteration, recurrent chromosomal rearrangement, or somatic driver was established. Large deletions should be considered if sequencing is negative, but karyotypic abnormalities are not a characteristic cause. No genetic anticipation has been reported.

5. Environmental information

FGD is not attributed to toxins, radiation, pollution, smoking, alcohol, diet, occupation, or infectious agents. Infection is a trigger of decompensation, not an etiologic agent. Lifestyle management centers on regular dosing, adequate intake during illness, avoidance of prolonged fasting, rapid treatment of vomiting or fever, and carrying emergency hydrocortisone. No zoonotic or transmissible component exists. (refaei2018familialglucocorticoiddeficiency pages 1-2, refaei2018familialglucocorticoiddeficiency pages 2-2)

6. Mechanism and pathophysiology

Upstream causal chain: MC2R/MRAP disease

  1. Biallelic MC2R or MRAP loss impairs ACTH receptor surface expression or function in adrenal cortical cells.
  2. ACTH-induced Gs–adenylyl cyclase–cAMP–PKA signaling falls.
  3. Cholesterol mobilization and steroidogenic enzyme expression are insufficient.
  4. Cortisol production declines.
  5. Reduced glucocorticoid feedback increases hypothalamic CRH and pituitary ACTH.
  6. ACTH/POMC-derived melanocortin activity produces hyperpigmentation, while cortisol deficiency causes fasting intolerance, hypoglycemia, poor stress response, and crisis. MRAP-null states generally manifest earlier than partially functional MC2R missense disease. (chung2010phenotypiccharacteristicsof pages 1-2, chung2010phenotypiccharacteristicsof pages 4-5)

Suggested GO biological processes: response to ACTH; cAMP-mediated signaling; steroid hormone biosynthetic process; glucocorticoid biosynthetic process; cholesterol transport; regulation of hormone secretion. Exact GO identifiers should be release-verified.

Mitochondrial redox chain: NNT/TXNRD2 disease

NNT is an inner-mitochondrial-membrane enzyme that supplies NADPH. NADPH maintains glutathione and thioredoxin antioxidant systems. NNT loss lowers reducing capacity, permits chronic ROS excess, and promotes oxidative injury/apoptosis in highly steroidogenic adrenal cells. TXNRD2 affects the same antioxidant network downstream. (malikova2014novelinsightinto pages 7-8, malikova2014novelinsightinto pages 11-12, ferreux2023testicularimpairmentin pages 1-2)

The 2023 report states in its abstract that “NNT encodes an inner mitochondrial membrane protein that produces large amounts of NADPH.” It then links NNT deficiency to ROS imbalance and extra-adrenal gonadal damage. (ferreux2023testicularimpairmentin pages 1-2)

In the detailed analysis, NNT was estimated to supply about 50% of required mitochondrial NADPH. Chronic ROS excess was proposed to cause progressive germ-cell degeneration. NNT-deficient mice showed testicular atrophy, smaller seminiferous tubules, increased degenerating and TUNEL-positive germ cells, and increased 8-OHdG, supporting—not proving—the human causal chain. (ferreux2023testicularimpairmentin pages 6-7)

Suggested GO terms: mitochondrial transmembrane transport; NADPH regeneration; cellular response to oxidative stress; glutathione metabolic process; thioredoxin-disulfide reductase activity; apoptotic process. Cell Ontology suggestions: adrenal cortical cell; steroid-producing cell; Leydig cell; Sertoli cell; male germ cell.

Partial steroidogenesis defects

STAR moves cholesterol to the inner mitochondrial membrane; CYP11A1 converts cholesterol to pregnenolone. Partial loss restricts the first steps shared by all adrenal steroids. Because residual activity varies by tissue and developmental stage, patients may resemble isolated FGD or develop mineralocorticoid and gonadal abnormalities. CYP11A1 missplicing demonstrates that protein-coding prediction alone may miss the true mechanism. (maharaj2019predictedbenignand pages 3-3, guran2016rarecausesof pages 4-6, buonocore2021geneticanalysisof pages 11-12)

Immune, tissue-damage, and omics findings

Classic FGD is not autoimmune or inflammatory. MCM4 disease may include natural-killer-cell deficiency, but that is a syndromic DNA-replication disorder rather than immune-mediated destruction of the adrenal. (malikova2014novelinsightinto pages 7-8, buonocore2021geneticanalysisof pages 11-12)

No robust FGD-specific patient transcriptome, proteome, metabolome, lipidome, single-cell atlas, spatial-transcriptomic dataset, or integrated multi-omics signature was found. Functional evidence presently comes mainly from receptor-expression studies, RNA-splicing assays, patient fibroblasts/cells, and genetically deficient animals.

7. Anatomical structures affected

  • Primary organ: bilateral adrenal glands, especially steroidogenic cells of the adrenal cortex. Suggested anatomy: adrenal gland — UBERON:0002369; adrenal cortex and zona fasciculata terms should be release-verified.
  • Primary cell: adrenal cortical/steroidogenic cell; suggested CL:0002097 adrenal cortical cell subject to ontology verification.
  • Subcellular compartments: plasma membrane and secretory/signaling machinery for MC2R/MRAP; mitochondrion and inner mitochondrial membrane for NNT, TXNRD2, STAR, and CYP11A1; nuclear/DNA-replication machinery for MCM4.
  • Secondary organs: brain in hypoglycemic seizures/injury; skin through ACTH-driven pigmentation; liver and systemic metabolism during hypoglycemia; testes in some NNT-deficient males.
  • NNT gonadal localization: seminiferous tubules, germ cells, Sertoli-cell compartment, and possibly testicular adrenal-rest tissue. (ferreux2023testicularimpairmentin pages 1-2, ferreux2023testicularimpairmentin pages 6-7)
  • Lateralization: adrenal dysfunction is systemic/bilateral. Testicular adrenal-rest tumors may be unilateral or bilateral; the 2023 patient had a right-sided lesion but bilateral Sertoli-cell-only pathology. (ferreux2023testicularimpairmentin pages 1-2)

Suggested GO cellular components include plasma membrane, receptor complex, mitochondrion, mitochondrial inner membrane, and nuclear pore complex for the AAAS differential.

8. Temporal development

FGD is genetically present from conception but clinically variable. MRAP-FGD commonly appears neonatally or in early infancy; MC2R-FGD may present from infancy through adolescence, with a reported upper range of 16 years. NNT disease generally presented between six months and four years in the UK experience. Partial STAR/CYP11A1 disease may appear in childhood with ketotic hypoglycemia. (chung2010phenotypiccharacteristicsof pages 1-2, buonocore2021geneticanalysisof pages 11-12)

The untreated course is chronic with episodic acute decompensation. There is no spontaneous remission of confirmed monogenic FGD. Five children in the broader UK unresolved-PAI cohort experienced resolution without an identified genetic cause, underscoring that transient adrenal insufficiency should not be misclassified as FGD. Genetic disease requires lifelong replacement. (buonocore2021geneticanalysisof pages 1-2)

Critical periods are the neonatal/infant period, intercurrent infection, prolonged fasting, surgery, and puberty in NNT disease. Puberty is a surveillance window for gonadal decline; in the 2023 case, testosterone remained stable until age 31 and then declined rapidly over three years. (ferreux2023testicularimpairmentin pages 6-7)

9. Inheritance and population

Epidemiology

FGD is very rare, but no reliable population-wide prevalence, incidence, carrier frequency, sex ratio, or survival registry estimate was retrieved. Published percentages are referral-cohort proportions and should not be converted into cases per 100,000.

In the 62-patient FGD analysis, MC2R and MRAP defects were estimated to explain approximately 25% and 20% of FGD, respectively. In 2014, about 70% of FGD was considered genetically explained, although subsequent sequencing has expanded the spectrum. (chung2010phenotypiccharacteristicsof pages 1-2, malikova2014novelinsightinto pages 7-8)

Among 95 Turkish children with unexplained PAI, sequencing diagnosed 77 (81%): MC2R 25, MRAP 9, NNT 7, CYP11A1 9, STAR 11, with additional non-FGD genes. Among 155 UK pediatric unresolved-PAI referrals, 103 (66.5%) received a diagnosis; MC2R was most frequent at 30/155 (19.4%). These are strong arguments for sequencing but not epidemiologic prevalence estimates. (guran2016rarecausesof pages 1-2, buonocore2021geneticanalysisof pages 1-2)

Mendelian properties

  • Inheritance: autosomal recessive for classic MC2R/MRAP FGD and most expanded FGD genes.
  • Recurrence risk: for two confirmed heterozygous parents, each pregnancy has 25% affected, 50% carrier, and 25% unaffected/noncarrier probability.
  • Penetrance: appears high for clearly damaging biallelic variants but has not been quantified uniformly; age and severity vary.
  • Expressivity: variable, especially for missense or hypomorphic alleles and partial STAR/CYP11A1 disease.
  • Anticipation: not expected or reported.
  • Mosaicism: no established FGD-specific germline-mosaicism rate; residual recurrence risk after an apparently de novo finding should be discussed conventionally.
  • Founder effects: MC2R p.Ser74Ile in Irish/Scottish ancestry and regional Turkish CYP11A1/MRAP variants are documented examples. (guran2016rarecausesof pages 6-7, buonocore2021geneticanalysisof pages 5-6)
  • Sex: both sexes are genetically susceptible. Sex-specific consequences arise from gonadal steroidogenic involvement, particularly NNT-associated male infertility.

10. Diagnostics

Clinical and biochemical pathway

  1. Suspect FGD in a neonate or child with hyperpigmentation, recurrent fasting/illness hypoglycemia, unexplained seizures, failure to thrive, shock, or family history.
  2. Before steroids if clinically safe, measure serum cortisol and plasma ACTH, glucose, sodium, potassium, bicarbonate, renin, and aldosterone. Do not delay emergency treatment to obtain testing.
  3. Typical classic FGD: very low cortisol, markedly elevated ACTH, normal electrolytes, and preserved renin/aldosterone. Normal 17-hydroxyprogesterone and androgens help distinguish 21-hydroxylase deficiency. (refaei2018familialglucocorticoiddeficiency pages 1-2, refaei2018familialglucocorticoiddeficiency pages 2-2)
  4. If basal results are equivocal, perform a standard ACTH/cosyntropin stimulation test; an attenuated cortisol response supports primary adrenal insufficiency. (maharaj2019predictedbenignand pages 3-3)
  5. Assess mineralocorticoid function repeatedly because partial steroidogenic defects may salt-waste and some children receive fludrocortisone initially.
  6. Evaluate differential diagnoses and proceed to molecular testing.

No imaging, biopsy, EEG, EMG, or adrenal histopathology is required routinely. Imaging is directed by differential diagnosis or complications—for example, testicular ultrasonography in postpubertal NNT deficiency. (ferreux2023testicularimpairmentin pages 1-2, ferreux2023testicularimpairmentin pages 6-7)

Genetic testing strategy

A practical first-line test is a next-generation sequencing pediatric PAI/ACTH-resistance panel including at least MC2R, MRAP, NNT, TXNRD2, STAR, CYP11A1, AAAS, MCM4 and broader PAI genes such as NR0B1, ABCD1, NR5A1, SAMD9, SGPL1, and CDKN1C. Copy-number calling should be included. The Turkish study achieved an 81% yield with targeted NGS, while the UK series demonstrated that NGS improves yield where many genes overlap phenotypically. (guran2016rarecausesof pages 1-2, buonocore2021geneticanalysisof pages 1-2)

Population-specific single-variant testing may be economical when ancestry and phenotype strongly indicate a founder allele; three recurrent variants would have diagnosed 26% of families in the Turkish cohort. This should not replace panel analysis after a negative result. (guran2016rarecausesof pages 6-7)

If panel testing is negative, use trio WES or WGS, with reanalysis, deletion/duplication analysis, deep-intronic interrogation, and RNA studies. RNA sequencing or targeted transcript analysis is particularly useful for possible CYP11A1 splice variants. CMA, karyotyping, FISH, mitochondrial DNA testing, and repeat-expansion assays are not routine unless another phenotype indicates them. (maharaj2019predictedbenignand pages 3-3)

Differential diagnosis

Important alternatives include congenital adrenal hyperplasia; autoimmune Addison disease; X-linked adrenoleukodystrophy; NR0B1-related adrenal hypoplasia; Triple A syndrome; MIRAGE syndrome; mitochondrial and metabolic disease; infection/hemorrhage; and secondary/tertiary adrenal insufficiency. Alacrima and achalasia point toward AAAS; neurologic deterioration can suggest Triple A or adrenoleukodystrophy; genital anomalies, salt wasting, or gonadal dysfunction suggest a broader steroidogenic defect. (refaei2018familialglucocorticoiddeficiency pages 2-2, guran2016rarecausesof pages 1-2, buonocore2021geneticanalysisof pages 1-2)

Screening

FGD is not part of routine newborn screening. Once a familial genotype is known, cascade testing, carrier testing, prenatal diagnosis, and preimplantation genetic testing are technically feasible. Biochemical testing should accompany predictive testing where age-dependent presentation remains possible.

11. Outcome and prognosis

Untreated FGD can cause recurrent adrenal crises, hypoglycemic seizures, irreversible neurologic injury, shock, and death. Early diagnosis and reliable glucocorticoid replacement generally produce a favorable endocrine prognosis, reverse hyperpigmentation, normalize growth velocity, and prevent most crises. (chung2010phenotypiccharacteristicsof pages 4-5, refaei2018familialglucocorticoiddeficiency pages 1-2, refaei2018familialglucocorticoiddeficiency pages 2-2)

No valid FGD-specific 5-year survival, 10-year survival, life-expectancy, mortality-rate, disability, or quality-of-life statistic was found. Prognosis is driven by age at diagnosis, severity and duration of hypoglycemia, treatment adherence, emergency preparedness, access to injectable hydrocortisone, and genotype-specific extra-adrenal disease.

NNT deficiency may carry a distinct fertility prognosis despite well-controlled adrenal disease. In the 35-year-old man reported in 2023, eight months of intensified glucocorticoid treatment neither reduced the testicular adrenal-rest tumor nor restored sperm production; bilateral Sertoli-cell-only syndrome indicated irreversible germ-cell loss. The authors called this the first direct evidence of complete germ-line loss in an azoospermic NNT-deficient man. (ferreux2023testicularimpairmentin pages 1-2)

12. Treatment

Standard pharmacotherapy

Hydrocortisone is first-line lifelong replacement in children because it replaces deficient cortisol and has less growth-suppressive potency than long-acting glucocorticoids. A reported maintenance regimen was approximately 10 mg/m²/day, divided through the day and individualized clinically. Adequate therapy improves pigmentation and suppresses excessive ACTH, although complete ACTH normalization should not be pursued at the cost of glucocorticoid overtreatment. (refaei2018familialglucocorticoiddeficiency pages 1-2)

Suggested annotations:

  • Hydrocortisone: CHEBI:17650; NCIt concepts for hydrocortisone/glucocorticoid replacement should be release-verified.
  • Fludrocortisone: NCIt drug concept should be verified; indicated only for documented mineralocorticoid deficiency, salt wasting, or persistently abnormal renin/electrolytes.

Seven MC2R patients in the UK cohort initially received mineralocorticoid, and three later discontinued it after the molecular diagnosis clarified classic FGD physiology. This illustrates a real-world benefit of genotype-guided management. (buonocore2021geneticanalysisof pages 5-6)

Stress and emergency treatment

During febrile illness, significant injury, surgery, or systemic stress, hydrocortisone must be increased according to an adrenal-insufficiency sick-day protocol. One case report instructed doubling the dose with temperature above 38.5°C. Vomiting, severe weakness, altered consciousness, hypoglycemia, or shock requires immediate parenteral hydrocortisone, glucose as needed, isotonic fluid resuscitation, and emergency assessment. Families need injection training, an emergency card/medical alert, and medication supplies at home and school. (refaei2018familialglucocorticoiddeficiency pages 2-2)

Genotype-specific supportive care

  • NNT: monitor puberty, gonadotropins, testosterone/estradiol as appropriate, semen analysis, and testicular ultrasound. Discuss sperm cryopreservation or testicular sperm extraction early, before progressive loss. (ferreux2023testicularimpairmentin pages 1-2, ferreux2023testicularimpairmentin pages 6-7)
  • Partial STAR/CYP11A1: monitor renin, aldosterone, electrolytes, puberty, genital development, and fertility; add mineralocorticoid when indicated. (guran2016rarecausesof pages 1-2, guran2016rarecausesof pages 4-6)
  • MCM4/AAAS phenocopies: provide syndrome-specific immune, neurologic, gastrointestinal, or ophthalmic surveillance.

Advanced and experimental treatments

No approved gene therapy, CRISPR treatment, RNA therapy, cell therapy, immunotherapy, or surgery corrects classic FGD. Surgery is not a treatment for adrenal ACTH resistance. Modified-release hydrocortisone and continuous subcutaneous infusion are being studied or used in broader adrenal insufficiency, but disease-specific efficacy in FGD is unproven.

The ClinicalTrials.gov search found adrenal-insufficiency formulation or replacement studies, but no FGD-specific interventional study. Therefore, trials such as NCT06435481 (pediatric oral hydrocortisone formulations) are indirect and should not be presented as FGD trials.

13. Prevention

Primary prevention: there is no lifestyle or immunization strategy that prevents an inherited biallelic disorder. Reproductive options include carrier testing of relatives, genetic counseling, prenatal diagnosis, and preimplantation genetic testing.

Secondary prevention: cascade testing and early biochemical assessment of at-risk siblings can detect disease before severe hypoglycemia or crisis. Molecular diagnosis also supports presymptomatic testing and personalized mineralocorticoid decisions. (guran2016rarecausesof pages 1-2)

Tertiary prevention: daily replacement, sick-day dosing, avoidance of prolonged fasting, immediate management of vomiting, emergency injectable hydrocortisone, medical identification, school/work action plans, and perioperative steroid coverage prevent crisis and neurologic injury. In NNT disease, puberty-onward fertility monitoring and early cryopreservation seek to prevent irreversible reproductive loss. (refaei2018familialglucocorticoiddeficiency pages 2-2, ferreux2023testicularimpairmentin pages 1-2, ferreux2023testicularimpairmentin pages 6-7)

Routine vaccination should follow standard schedules; vaccines do not prevent FGD, although fever after vaccination may require ordinary sick-day management.

14. Other species and natural disease

No well-established naturally occurring companion-animal or wildlife disorder directly equivalent to human FGD was identified in the retrieved evidence. Accordingly, no defensible OMIA, breed/VBO, veterinary incidence, or zoonotic annotation can be supplied. FGD is not infectious and has no zoonotic transmission.

The relevant genes and mitochondrial redox systems are evolutionarily conserved. Mus musculus (NCBI Taxonomy 10090) is the best-supported comparative species in the retrieved literature. Ortholog-specific NCBI Gene identifiers should be obtained directly from NCBI rather than inferred from the clinical papers.

15. Model organisms and experimental systems

NNT-deficient mouse

NNT-deficient mice provide mechanistic support for gonadal oxidative injury. Reported findings include testicular atrophy, reduced seminiferous-tubule diameter, increased germ-cell degeneration, increased TUNEL-positive cells, and elevated 8-hydroxy-2′-deoxyguanosine. This model supports the NADPH–ROS–germ-cell-death chain observed in the 2023 human case. It does not fully establish the frequency or reversibility of human infertility. (ferreux2023testicularimpairmentin pages 6-7)

Cellular and in-vitro systems

  • MC2R/MRAP expression systems assess receptor trafficking, surface expression, ACTH binding, and cAMP signaling.
  • Patient fibroblasts or engineered cells can assess mitochondrial ROS, NADPH-dependent antioxidant function, and apoptosis in NNT/TXNRD2 disease.
  • Minigene and RNA assays are especially informative for CYP11A1 variants predicted to be benign or synonymous. (maharaj2019predictedbenignand pages 3-3)

No validated FGD adrenal organoid, patient-derived iPSC adrenal model, zebrafish disease model, or CRISPR screening platform was established from the retrieved literature. These remain promising research approaches rather than current clinical implementations.

Recent developments and expert interpretation

The most clinically important recent evidence retrieved was Ferreux et al., published March 2023, DOI 10.1186/s12610-022-00176-6. Its central conclusion was that NNT-associated disease may not remain adrenal-limited: progressive oxidative injury can destroy the male germ line even while adrenal replacement is adequate, so fertility surveillance should begin at puberty and preservation should be considered in early adulthood. (ferreux2023testicularimpairmentin pages 1-2, ferreux2023testicularimpairmentin pages 6-7)

No equally substantive FGD-specific 2024 cohort or therapeutic study was recovered. Thus, the current evidence base remains anchored by the May 2010 FGD1/FGD2 phenotype study, DOI 10.1111/j.1365-2265.2009.03663.x; the January 2016 Turkish nationwide cohort, DOI 10.1210/jc.2015-3250; the October 2019 CYP11A1 functional study, DOI 10.1210/js.2018-00130; and the May 2021 UK 25-year genetic study, DOI 10.1210/jendso/bvab086. (chung2010phenotypiccharacteristicsof pages 1-2, guran2016rarecausesof pages 1-2, maharaj2019predictedbenignand pages 3-3, buonocore2021geneticanalysisof pages 1-2)

Expert interpretation from these cohorts is consistent: phenotype alone can suggest a gene—very early onset for MRAP, tall stature for MC2R, ketotic hypoglycemia for partial STAR/CYP11A1, and postpubertal gonadal disease for NNT—but overlapping presentations make multigene sequencing essential. Molecular diagnosis is not merely descriptive: it guides mineralocorticoid use, anticipatory surveillance, reproductive counseling, and presymptomatic family testing. (guran2016rarecausesof pages 1-2, buonocore2021geneticanalysisof pages 11-12, buonocore2021geneticanalysisof pages 2-3)

Evidence limitations

  1. FGD is so rare that phenotype frequencies, penetrance, population prevalence, mortality, and quality of life remain poorly quantified.
  2. Large sequencing cohorts combine classical FGD with broader pediatric primary adrenal insufficiency; their gene percentages are referral-cohort statistics.
  3. Some requested identifiers, HGNC IDs, current ClinVar assertions, gnomAD frequencies, and ontology codes were not present in the retrieved primary literature and require direct, release-specific database validation.
  4. Direct abstract quotations were limited to short passages to preserve accuracy; PMIDs were not exposed in the retrieved records, so DOI URLs are supplied rather than guessed PMIDs.
  5. Disease-specific advanced-omics, natural-animal-disease, and interventional-trial evidence is currently absent or insufficient.

References

  1. (chung2010phenotypiccharacteristicsof pages 1-2): Teng‐Teng L. L. Chung, Li F. Chan, Louise A. Metherell, and Adrian J. L. Clark. Phenotypic characteristics of familial glucocorticoid deficiency (fgd) type 1 and 2. Clinical Endocrinology, 72:589-594, May 2010. URL: https://doi.org/10.1111/j.1365-2265.2009.03663.x, doi:10.1111/j.1365-2265.2009.03663.x. This article has 110 citations and is from a peer-reviewed journal.

  2. (malikova2014novelinsightinto pages 7-8): Jana Malikova and Christa Flück. Novel insight into etiology, diagnosis and management of primary adrenal insufficiency. Hormone Research in Paediatrics, 82:145-157, Aug 2014. URL: https://doi.org/10.1159/000363107, doi:10.1159/000363107. This article has 73 citations and is from a peer-reviewed journal.

  3. (guran2016rarecausesof pages 4-6): Tulay Guran, Federica Buonocore, Nurcin Saka, Mehmet Nuri Ozbek, Zehra Aycan, Abdullah Bereket, Firdevs Bas, Sukran Darcan, Aysun Bideci, Ayla Guven, Korcan Demir, Aysehan Akinci, Muammer Buyukinan, Banu Kucukemre Aydin, Serap Turan, Sebahat Yilmaz Agladioglu, Zeynep Atay, Zehra Yavas Abali, Omer Tarim, Gonul Catli, Bilgin Yuksel, Teoman Akcay, Metin Yildiz, Samim Ozen, Esra Doger, Huseyin Demirbilek, Ahmet Ucar, Emregul Isik, Bayram Ozhan, Semih Bolu, Ilker Tolga Ozgen, Jenifer P. Suntharalingham, and John C. Achermann. Rare causes of primary adrenal insufficiency: genetic and clinical characterization of a large nationwide cohort. The Journal of Clinical Endocrinology & Metabolism, 101:284-292, Jan 2016. URL: https://doi.org/10.1210/jc.2015-3250, doi:10.1210/jc.2015-3250. This article has 223 citations.

  4. (refaei2018familialglucocorticoiddeficiency pages 2-2): A. Refaei, Amer O. Al-Ali, M. Soeid, N. A. Jurayyan, B. Alenazi, and Taleb Ra. Familial glucocorticoid deficiency presenting as progressive hyperpigmentation: a case report. journal of Clinical Case Reports, 8:1-2, May 2018. URL: https://doi.org/10.4172/2165-7920.10001120, doi:10.4172/2165-7920.10001120. This article has 0 citations.

  5. (malikova2014novelinsightinto pages 11-12): Jana Malikova and Christa Flück. Novel insight into etiology, diagnosis and management of primary adrenal insufficiency. Hormone Research in Paediatrics, 82:145-157, Aug 2014. URL: https://doi.org/10.1159/000363107, doi:10.1159/000363107. This article has 73 citations and is from a peer-reviewed journal.

  6. (guran2016rarecausesof pages 6-7): Tulay Guran, Federica Buonocore, Nurcin Saka, Mehmet Nuri Ozbek, Zehra Aycan, Abdullah Bereket, Firdevs Bas, Sukran Darcan, Aysun Bideci, Ayla Guven, Korcan Demir, Aysehan Akinci, Muammer Buyukinan, Banu Kucukemre Aydin, Serap Turan, Sebahat Yilmaz Agladioglu, Zeynep Atay, Zehra Yavas Abali, Omer Tarim, Gonul Catli, Bilgin Yuksel, Teoman Akcay, Metin Yildiz, Samim Ozen, Esra Doger, Huseyin Demirbilek, Ahmet Ucar, Emregul Isik, Bayram Ozhan, Semih Bolu, Ilker Tolga Ozgen, Jenifer P. Suntharalingham, and John C. Achermann. Rare causes of primary adrenal insufficiency: genetic and clinical characterization of a large nationwide cohort. The Journal of Clinical Endocrinology & Metabolism, 101:284-292, Jan 2016. URL: https://doi.org/10.1210/jc.2015-3250, doi:10.1210/jc.2015-3250. This article has 223 citations.

  7. (guran2016rarecausesof pages 4-4): Tulay Guran, Federica Buonocore, Nurcin Saka, Mehmet Nuri Ozbek, Zehra Aycan, Abdullah Bereket, Firdevs Bas, Sukran Darcan, Aysun Bideci, Ayla Guven, Korcan Demir, Aysehan Akinci, Muammer Buyukinan, Banu Kucukemre Aydin, Serap Turan, Sebahat Yilmaz Agladioglu, Zeynep Atay, Zehra Yavas Abali, Omer Tarim, Gonul Catli, Bilgin Yuksel, Teoman Akcay, Metin Yildiz, Samim Ozen, Esra Doger, Huseyin Demirbilek, Ahmet Ucar, Emregul Isik, Bayram Ozhan, Semih Bolu, Ilker Tolga Ozgen, Jenifer P. Suntharalingham, and John C. Achermann. Rare causes of primary adrenal insufficiency: genetic and clinical characterization of a large nationwide cohort. The Journal of Clinical Endocrinology & Metabolism, 101:284-292, Jan 2016. URL: https://doi.org/10.1210/jc.2015-3250, doi:10.1210/jc.2015-3250. This article has 223 citations.

  8. (buonocore2021geneticanalysisof pages 5-6): Federica Buonocore, Avinaash Maharaj, Younus Qamar, Katrin Koehler, Jenifer P Suntharalingham, Li F Chan, Bruno Ferraz-de-Souza, Claire R Hughes, Lin Lin, Rathi Prasad, Jeremy Allgrove, Edward T Andrews, Charles R Buchanan, Tim D Cheetham, Elizabeth C Crowne, Justin H Davies, John W Gregory, Peter C Hindmarsh, Tony Hulse, Nils P Krone, Pratik Shah, M Guftar Shaikh, Catherine Roberts, Peter E Clayton, Mehul T Dattani, N Simon Thomas, Angela Huebner, Adrian J Clark, Louise A Metherell, and John C Achermann. Genetic analysis of pediatric primary adrenal insufficiency of unknown etiology: 25 years’ experience in the uk. Journal of the Endocrine Society, May 2021. URL: https://doi.org/10.1210/jendso/bvab086, doi:10.1210/jendso/bvab086. This article has 66 citations and is from a peer-reviewed journal.

  9. (buonocore2021geneticanalysisof pages 11-12): Federica Buonocore, Avinaash Maharaj, Younus Qamar, Katrin Koehler, Jenifer P Suntharalingham, Li F Chan, Bruno Ferraz-de-Souza, Claire R Hughes, Lin Lin, Rathi Prasad, Jeremy Allgrove, Edward T Andrews, Charles R Buchanan, Tim D Cheetham, Elizabeth C Crowne, Justin H Davies, John W Gregory, Peter C Hindmarsh, Tony Hulse, Nils P Krone, Pratik Shah, M Guftar Shaikh, Catherine Roberts, Peter E Clayton, Mehul T Dattani, N Simon Thomas, Angela Huebner, Adrian J Clark, Louise A Metherell, and John C Achermann. Genetic analysis of pediatric primary adrenal insufficiency of unknown etiology: 25 years’ experience in the uk. Journal of the Endocrine Society, May 2021. URL: https://doi.org/10.1210/jendso/bvab086, doi:10.1210/jendso/bvab086. This article has 66 citations and is from a peer-reviewed journal.

  10. (chung2010phenotypiccharacteristicsof pages 4-5): Teng‐Teng L. L. Chung, Li F. Chan, Louise A. Metherell, and Adrian J. L. Clark. Phenotypic characteristics of familial glucocorticoid deficiency (fgd) type 1 and 2. Clinical Endocrinology, 72:589-594, May 2010. URL: https://doi.org/10.1111/j.1365-2265.2009.03663.x, doi:10.1111/j.1365-2265.2009.03663.x. This article has 110 citations and is from a peer-reviewed journal.

  11. (buonocore2021geneticanalysisof pages 1-2): Federica Buonocore, Avinaash Maharaj, Younus Qamar, Katrin Koehler, Jenifer P Suntharalingham, Li F Chan, Bruno Ferraz-de-Souza, Claire R Hughes, Lin Lin, Rathi Prasad, Jeremy Allgrove, Edward T Andrews, Charles R Buchanan, Tim D Cheetham, Elizabeth C Crowne, Justin H Davies, John W Gregory, Peter C Hindmarsh, Tony Hulse, Nils P Krone, Pratik Shah, M Guftar Shaikh, Catherine Roberts, Peter E Clayton, Mehul T Dattani, N Simon Thomas, Angela Huebner, Adrian J Clark, Louise A Metherell, and John C Achermann. Genetic analysis of pediatric primary adrenal insufficiency of unknown etiology: 25 years’ experience in the uk. Journal of the Endocrine Society, May 2021. URL: https://doi.org/10.1210/jendso/bvab086, doi:10.1210/jendso/bvab086. This article has 66 citations and is from a peer-reviewed journal.

  12. (refaei2018familialglucocorticoiddeficiency pages 1-2): A. Refaei, Amer O. Al-Ali, M. Soeid, N. A. Jurayyan, B. Alenazi, and Taleb Ra. Familial glucocorticoid deficiency presenting as progressive hyperpigmentation: a case report. journal of Clinical Case Reports, 8:1-2, May 2018. URL: https://doi.org/10.4172/2165-7920.10001120, doi:10.4172/2165-7920.10001120. This article has 0 citations.

  13. (guran2016rarecausesof pages 1-2): Tulay Guran, Federica Buonocore, Nurcin Saka, Mehmet Nuri Ozbek, Zehra Aycan, Abdullah Bereket, Firdevs Bas, Sukran Darcan, Aysun Bideci, Ayla Guven, Korcan Demir, Aysehan Akinci, Muammer Buyukinan, Banu Kucukemre Aydin, Serap Turan, Sebahat Yilmaz Agladioglu, Zeynep Atay, Zehra Yavas Abali, Omer Tarim, Gonul Catli, Bilgin Yuksel, Teoman Akcay, Metin Yildiz, Samim Ozen, Esra Doger, Huseyin Demirbilek, Ahmet Ucar, Emregul Isik, Bayram Ozhan, Semih Bolu, Ilker Tolga Ozgen, Jenifer P. Suntharalingham, and John C. Achermann. Rare causes of primary adrenal insufficiency: genetic and clinical characterization of a large nationwide cohort. The Journal of Clinical Endocrinology & Metabolism, 101:284-292, Jan 2016. URL: https://doi.org/10.1210/jc.2015-3250, doi:10.1210/jc.2015-3250. This article has 223 citations.

  14. (ferreux2023testicularimpairmentin pages 1-2): Lucile Ferreux, Yasmine Boumerdassi, Emmanuel Dulioust, Xavier Bertagna, Florence Roucher-Boulez, Mathilde Bourdon, Nicolas Thiounn, and Catherine Patrat. Testicular impairment in primary adrenal insufficiency caused by nicotinamide nucleotide transhydrogenase (nnt) deficiency - a case report: implication of oxidative stress and importance of fertility preservation. Basic and Clinical Andrology, Mar 2023. URL: https://doi.org/10.1186/s12610-022-00176-6, doi:10.1186/s12610-022-00176-6. This article has 3 citations.

  15. (ferreux2023testicularimpairmentin pages 6-7): Lucile Ferreux, Yasmine Boumerdassi, Emmanuel Dulioust, Xavier Bertagna, Florence Roucher-Boulez, Mathilde Bourdon, Nicolas Thiounn, and Catherine Patrat. Testicular impairment in primary adrenal insufficiency caused by nicotinamide nucleotide transhydrogenase (nnt) deficiency - a case report: implication of oxidative stress and importance of fertility preservation. Basic and Clinical Andrology, Mar 2023. URL: https://doi.org/10.1186/s12610-022-00176-6, doi:10.1186/s12610-022-00176-6. This article has 3 citations.

  16. (buonocore2021geneticanalysisof pages 2-3): Federica Buonocore, Avinaash Maharaj, Younus Qamar, Katrin Koehler, Jenifer P Suntharalingham, Li F Chan, Bruno Ferraz-de-Souza, Claire R Hughes, Lin Lin, Rathi Prasad, Jeremy Allgrove, Edward T Andrews, Charles R Buchanan, Tim D Cheetham, Elizabeth C Crowne, Justin H Davies, John W Gregory, Peter C Hindmarsh, Tony Hulse, Nils P Krone, Pratik Shah, M Guftar Shaikh, Catherine Roberts, Peter E Clayton, Mehul T Dattani, N Simon Thomas, Angela Huebner, Adrian J Clark, Louise A Metherell, and John C Achermann. Genetic analysis of pediatric primary adrenal insufficiency of unknown etiology: 25 years’ experience in the uk. Journal of the Endocrine Society, May 2021. URL: https://doi.org/10.1210/jendso/bvab086, doi:10.1210/jendso/bvab086. This article has 66 citations and is from a peer-reviewed journal.

  17. (maharaj2019predictedbenignand pages 3-3): A. Maharaj, Federica Buonocore, E. Meimaridou, G. Ruiz-Babot, L. Guasti, Hwei-Ming Peng, Cameron P Capper, Neikelyn Burgos-Tirado, R. Prasad, C. Hughes, Ashwini Maudhoo, E. Crowne, T. Cheetham, C. Brain, Jenifer P. Suntharalingham, Niccolò Striglioni, B. Yuksel, F. Gurbuz, Sangay Gupta, R. Lindsay, R. Couch, H. Spoudeas, T. Guran, S. Johnson, D. Fowler, L. Conwell, A. McInerney-Leo, D. Drui, B. Cariou, J. López-Siguero, M. Harris, E. Duncan, P. Hindmarsh, R. Auchus, M. Donaldson, J. Achermann, and L. Metherell. Predicted benign and synonymous variants in cyp11a1 cause primary adrenal insufficiency through missplicing. Journal of the Endocrine Society, 3:201-221, Oct 2019. URL: https://doi.org/10.1210/js.2018-00130, doi:10.1210/js.2018-00130. This article has 30 citations and is from a peer-reviewed journal.

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