The adrenal cortex produces three families of steroid hormones: mineralocorticoids, glucocorticoids and adrenal androgen precursors. Each family has its own synthesis route, its own control system and its own actions on target tissues.
That is the idea the whole topic hangs on: nearly every disorder of the cortex is a deficiency or excess of one or more of these hormones. The same enzymes and control loops that set normal output are the points where production can fall or rise, so the biology of the cortex explains how it goes wrong.
Which note answers which question?
If the gland is unfamiliar, start with the structure note. Then read in order: what the cortex makes, then glucocorticoid control and synthesis, then aldosterone and its separate control system, then the fate of cortisol in the body and testing of the axis.
- The Adrenal Cortex: Structure and Hormone Families: the three zones of the cortex, the enzyme difference that separates them, and the actions of mineralocorticoids, glucocorticoids and adrenal androgens.
- The HPA Axis and the Control of Glucocorticoid Production: how CRH and ACTH drive cortisol, how a circadian rhythm shapes it, and how negative feedback keeps it within range.
- Steroid Hormone Synthesis in the Adrenal Cortex: the shared pathway from ACTH and cholesterol, and the CYP family of steroid-building enzymes that lead to cortisol, aldosterone and adrenal androgens.
- Aldosterone Secretion and the RAAS: aldosterone is controlled by the renin-angiotensin-aldosterone system (RAAS), a control system separate from the one for cortisol. The macula densa sets renin release, angiotensin II raises aldosterone, and potassium switches on aldosterone synthase in the zona glomerulosa.
- Cortisol Metabolism and Glucocorticoid Receptor Action: how cortisol is carried in blood, how 11β-hydroxysteroid dehydrogenase (11β-HSD) enzymes switch it on or off in tissues, and how it acts through the glucocorticoid receptor.
- Assessment of Adrenal Function: how the feedback loop is used to test the axis, through dexamethasone suppression, ACTH stimulation with cosyntropin and the insulin tolerance test.
Before any hormone can be too low or too high, what does the cortex make, and where in the gland is each family made?