Physiology · Short notes

Endocrine Physiology: Short Notes & Cheat Sheet

Hormone classes and receptors, the hypothalamic–pituitary axes, thyroid, parathyroid, adrenal and pancreatic hormones, and classic endocrine disorders.

Attempt Endocrine Physiology MCQs

Short notes

Read these before you attempt the topic's MCQs.

Anterior pituitary hormones and their targets

Each hormone drives a target gland, which feeds back to switch the pituitary off.

Hormones and receptors

Peptide hormones (insulin, glucagon, ADH, GH) and catecholamines act on cell-surface receptors through second messengers such as cAMP.
Steroid hormones (cortisol, aldosterone, sex steroids) and thyroid hormones act on intracellular receptors and change gene transcription, so they act more slowly.
Most axes are controlled by negative feedback: the end hormone suppresses its own releasing hormones.

Hypothalamus and pituitary

The hypothalamus releases TRH, CRH, GnRH, GHRH, somatostatin (inhibits GH) and dopamine (inhibits prolactin).
The anterior pituitary secretes FSH, LH, ACTH, TSH, prolactin and growth hormone.
The posterior pituitary releases ADH and oxytocin, which are made in the hypothalamus (supraoptic and paraventricular nuclei).
Growth hormone acts largely through IGF-1 from the liver. Excess causes gigantism before the growth plates close and acromegaly after.

Glands

Thyroid: mainly secretes T4, which is converted to the more active T3 in tissues. Parafollicular C cells secrete calcitonin, which lowers calcium.
PTH raises blood calcium by bone resorption, renal calcium reabsorption and activating vitamin D; it also increases phosphate excretion.
Adrenal cortex, outer to inner: zona glomerulosa (aldosterone), fasciculata (cortisol) and reticularis (androgens). The medulla makes adrenaline and noradrenaline.
Pancreatic islets: β cells make insulin (lowers glucose, moves K⁺ into cells), α cells glucagon and δ cells somatostatin.
Disorders: Cushing's (excess cortisol), Addison's (adrenal insufficiency), Conn's (excess aldosterone), Graves' (TSH-receptor antibodies), Hashimoto's (autoimmune hypothyroidism), phaeochromocytoma (catecholamine-secreting tumour).

Cheat sheet

High-yield facts in one place. Cover the right-hand column and test yourself.

Adrenal zones

Zone	Hormone
Zona glomerulosa	Aldosterone (salt)
Zona fasciculata	Cortisol (sugar)
Zona reticularis	Androgens (sex)
Medulla	Adrenaline, noradrenaline

Endocrine disorders

Disorder	Cause
Cushing's syndrome	Excess cortisol
Addison's disease	Primary adrenal insufficiency
Conn's syndrome	Excess aldosterone
Graves' disease	TSH-receptor stimulating antibodies
Hashimoto's thyroiditis	Autoimmune hypothyroidism
Acromegaly	GH excess after growth plates close
Central diabetes insipidus	ADH deficiency

Memory aids

Salt, Sugar, Sex — the deeper you go, the sweeter it gets: Adrenal cortex from outside in: aldosterone, cortisol, androgens (GFR: glomerulosa, fasciculata, reticularis).
FLAT PiG: Anterior pituitary hormones: FSH, LH, ACTH, TSH, Prolactin, GH.

Exam traps

ADH and oxytocin are made in the hypothalamus; the posterior pituitary only stores and releases them.
Thyroid hormones act on intracellular receptors, like steroids, even though they are amines.
Dopamine inhibits prolactin; dopamine antagonists can cause galactorrhoea.
Calcitonin lowers calcium; PTH raises it.

Revised? Now test yourself.

Attempt the Endocrine Physiology MCQs while the notes are fresh. Anything you get wrong is saved to your incorrect list for the next revision round.