This is a mechanism module, not a specific disease. Disorder entries reference individual nodes via conforms_to (e.g., "hypothyroidism_thyroid_hormone_deficiency#Thyroid Hormone Insufficiency"). Conforming nodes should substitute the disorder-specific cause of reduced hormone synthesis: autoimmune thyroiditis, iodine deficiency, dyshormonogenesis (TPO/TG/NIS/DUOX2 defects), or central hypothyroidism (in which low TSH rather than the compensatory rise distinguishes the feedback arm).
Impaired Thyroid Hormone Synthesis
trigger
The conserved initiating lesion is impaired synthesis of thyroid hormone by thyroid follicular cells, whether from autoimmune destruction of the gland, inadequate iodine substrate, or genetic defects in the hormone biosynthetic machinery. Iatrogenic causes (thyroidectomy, radioiodine, antithyroid drugs) act at the same point.
Used by disorders
Sheehan Syndrome
as Central Hypothyroidism from Thyroid-Stimulating Hormone Deficiency
Downstream
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Thyroid Hormone Insufficiency
Show evidence (2 references)
"Primary hypothyroidism typically is a result of autoimmune thyroiditis or iodine deficiency and is assessed by measurement of the thyroid-stimulating hormone (TSH) level."
Identifies autoimmune thyroiditis and iodine deficiency as the principal causes of impaired hormone synthesis, the conserved initiating lesion. Evidence source is OTHER because this is a review article.
"The leading causes of hypothyroidism in older adults are iatrogenic, Hashimoto's thyroiditis, and medications."
Confirms the spectrum of upstream causes (iatrogenic, autoimmune, drug-induced) that converge on reduced hormone synthesis. Evidence source is OTHER because this is a narrative review.
Thyroid Hormone Insufficiency
amplifier
Reduced synthesis lowers circulating T4 and T3. In primary hypothyroidism the loss of negative feedback drives a compensatory rise in pituitary thyroid-stimulating hormone (TSH), the biochemical hallmark used in diagnosis.
Downstream
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Reduced Thyroid Hormone Action at Peripheral Sites
Show evidence (1 reference)
"This level usually is elevated in patients with hypothyroidism and low in patients with hyperthyroidism."
Describes the compensatory TSH elevation that signals thyroid hormone insufficiency in primary hypothyroidism. Evidence source is OTHER because this is a review article.
Reduced Thyroid Hormone Action at Peripheral Sites
central effector
Insufficient circulating hormone reduces thyroid hormone signaling and action in peripheral target tissues. Because thyroid hormone metabolism and activity decline together, target tissues throughout the body receive diminished thyroid hormone stimulus.
Show evidence (1 reference)
"Thyroid function declines over time due to physiological changes in the thyroid stimulating hormone signaling, iodine absorption and metabolism, thyroid hormone metabolism, and activity at peripheral sites."
Identifies thyroid hormone activity at peripheral sites as a component of thyroid function whose decline mediates the systemic effects of hormone deficiency. Evidence source is OTHER because this is a narrative review.