🧂 Endocrine System Lesson

GFR: three zones, "Salt, Sugar, Sex"

The adrenal cortex has three distinct zones, each producing a completely different class of hormone — and the mnemonic tells you the order from outside to inside.

Glomer.

Fascic.

Reticul.

📖 Full Breakdown

Three zones, outside to inside, each with a distinct hormone class

"Salt, Sugar, Sex — the deeper you go" pairs directly with GFR in anatomical order.

Zona Glomerulosa

Outermost — Salt

Produces mineralocorticoids, primarily aldosterone, which drives sodium retention and potassium secretion, directly regulating blood pressure.

Zona Fasciculata

Middle (largest zone) — Sugar

Produces glucocorticoids, primarily cortisol — the body's main stress hormone, covered in depth in the next lesson.

Zona Reticularis

Innermost — Sex

Produces androgens (DHEA), weak sex hormones that get converted to more potent forms in peripheral tissues.

🩺 Clinical / Exam Application

A patient with adrenal insufficiency (Addison's disease) presents with low blood pressure, low sodium, and high potassium. All three findings trace back to a single zone: the zona glomerulosa's aldosterone is deficient, so sodium isn't being retained (causing hyponatremia and low blood volume/pressure) and potassium isn't being excreted (causing hyperkalemia). Knowing which zone produces which hormone class explains the entire electrolyte picture from one diagnosis.

⚠️ Exam Alert

Addison's disease (adrenal insufficiency, low cortisol + aldosterone) and Cushing's syndrome (excess cortisol) are frequently paired as opposite exam scenarios — know that Addison's often shows bronze skin pigmentation (from elevated ACTH cross-reacting with melanin receptors) while Cushing's shows moon face and buffalo hump.

🚧 Common Trap

Don't confuse Cushing's disease (a pituitary tumor causing excess ACTH, which then causes excess cortisol) with Cushing's syndrome (the general term for excess cortisol from any cause, including exogenous steroid medication). Disease specifically implies a pituitary cause; syndrome is the broader umbrella term.

✅ Quick Check

Using the GFR order, name each adrenal cortex zone from outside to inside and the hormone class each one produces.

📝 Exam Prep

Common Exam Questions

❓ What are the three zones of the adrenal cortex and what does each produce?

✅ Zona Glomerulosa (outer) produces mineralocorticoids like aldosterone. Zona Fasciculata (middle) produces glucocorticoids like cortisol. Zona Reticularis (inner) produces androgens like DHEA.

❓ What is Cushing's syndrome and what causes it?

✅ Cushing's syndrome is excess cortisol. Causes include exogenous steroid use (most common), a pituitary adenoma overproducing ACTH (Cushing's disease specifically), or an adrenal tumor. Signs include moon face, buffalo hump, central obesity, and purple striae.