Endocrine Disorders and Hormone Function

A compilation of key vocabulary terms and definitions related to endocrine disorders and hormone functions, designed to aid in understanding and retention for exam preparation.

Negative Feedback Loop

A regulatory mechanism in which an increase or decrease in hormone levels leads to opposite effects in hormone production.

ACTH

Adrenocorticotropic hormone, produced by the pituitary gland, stimulates the adrenal cortex to release cortisol.

ACTH stimulation test is used in the workup of what?

Hypocortisolism

If ACTH does not cause an increase in serum cortisol, the problem is with what?

Adrenal hypofunction

If ACTH causes an increase in serum cortisol, the problem is with what?

hypopituitarism or hypothalamic dysfunction

TRH stimulation test focuses on which area?

Pituitary gland/response

Normal response for a TRH stimulation test?

You would give TRH and measure TSH. normal response: TSH ↑

TSH Stimulation Test

Give TSH, measure T4. Normal response: : T4 ↑

No response to the TSH stimulation test shows what?

Thyroid gland failure (primary hypothyroidism) 

Hypofunctioning Disorder

A condition where there is insufficient hormone production from a gland.

Stimulation Test

A diagnostic method that evaluates the functioning of an endocrine gland (hypofunctioning disorders) by measuring its response to administered hormones.

TRH

Thyrotropin-releasing hormone, released by the hypothalamus to stimulate TSH production in the pituitary gland.

TSH

Thyroid-stimulating hormone, produced by the pituitary gland, that stimulates the thyroid gland to produce T3 and T4.

PIT—>Target fails means what in hypopituitarism?

PItuitary fails, target glands (thyroid, adrenal, gonads) fail next

Sheehan syndrome

• pregnancy-related infarction of the pituitary gland 

• Gland doubles in size during pregnancy, but blood supply does not increase significantly; blood loss during parturition precipitates infarction 

• Presents as poor lactation, loss of pubic hair, and fatigue

Empty sella syndrome-congenital defect

• The pituitary gland is "absent" (empty sella) on imaging

  • The sella turcica is known as “the seat” of the pituitary

Hypopituitarism

A condition where the pituitary gland fails to produce one or more of its hormones, affecting various endocrine functions.

Thyroid Suppression Test

• A test that assesses the thyroid's functionality by measuring its response to administered thyroid hormones.

• T3 turns TSH off!

• Give T3, check if TSH decreases (normal response)

Providing Low-dose dexamethasone in Suppression tests

It evaluates hypercortisolism d/t pituitary, adrenal, or ectopic

If there are suppressed levels after administration, there is a normal response

Graves' Disease

• An autoimmune disorder that leads to hyperthyroidism, characterized by the stimulation of the TSH receptor by autoantibodies.

• If TSH is not suppressed after administering T3, this condition would be suggested

Cushing Syndrome and what would you see in a suppression test?

• A condition caused by excess cortisol production, leading to symptoms such as weight gain, hypertension, and glucose intolerance.

• Suppression test: cortisol fails to suppress

Pituitary adenoma

Benign tumor of anterior pituitary cells

Functional (hormone-producing) pituitary adenoma

• Present with features based on the hormone produced 

  • E.g. acromegaly d/t excess growth hormone (GH) production

Nonfunctional tumors in pituitary adenoma & examples

Present with mass effect (tumor pushing on or displacing tissue)

• Such as bitemporal hemianopsia or hypopituitarism

Addison's Disease

A disorder characterized by insufficient production of adrenal hormones, often revealing symptoms like fatigue, weight loss, and hyperpigmentation.

Pheochromocytoma

A tumor of the adrenal medulla that results in excessive catecholamine secretion, leading to episodic hypertension and other symptoms.

Diabetes Insipidus

A condition resulting from the deficiency of ADH, leading to excessive thirst and polyuria.

Hyperthyroidism

An endocrine disorder where the thyroid gland is overactive, resulting in elevated levels of thyroid hormones.

Hypothyroidism

A condition characterized by insufficient production of thyroid hormones, resulting in a metabolism slowdown and various symptoms.

Congenital Adrenal Hyperplasia (CAH)

A genetic defect that affects adrenal hormone production, often leading to variability in symptom presentation based on hormone level.

T3 and T4

Triiodothyronine (T3) and Thyroxine (T4) are thyroid hormones critical for regulating metabolism.

Metanephrines

Metabolites of catecholamines used as biomarkers for diagnosing pheochromocytoma.