30/01/2026
Primary vs Secondary adrenal insufficiency!
Hyper-KALEMIA & Hyper-PIGMENTATION → ONLY Primary (Addison’s disease).
You’ve hit the two "Big H's" that make clinical diagnosis much easier.
1. Hyperpigmentation: The POMC Connection.
In Primary AI, the pituitary is screaming at the adrenals to wake up. It pumps out massive amounts of ACTH.
• The Mechanism: ACTH is derived from a precursor molecule called Pro-opiomelanocortin (POMC). When POMC is cleaved to make ACTH, it also produces Melanocyte-Stimulating Hormone (MSH).
• The Result: High ACTH = High MSH = Bronzing of the skin (especially in skin folds, scars, and gums).
• Secondary AI: The problem is the pituitary; ACTH is low, so there's no MSH surge to darken the skin.
2. Hyperkalemia: The Aldosterone Factor
This is the life-threatening distinction.
• Primary AI: The entire adrenal cortex is typically destroyed. This means you lose Cortisol AND Aldosterone. Since aldosterone's job is to dump Potassium (K^+) and keep Sodium (Na^+), losing it leads to Hyperkalemia and hyponatremia.
• Secondary AI: The pituitary only controls Cortisol (via ACTH). The Renin-Angiotensin-Aldosterone System (RAAS) is what actually controls aldosterone, and it stays intact. Therefore, potassium levels usually remain normal.
If a patient has signs of adrenal insufficiency but also has other "down" hormones (like TSH or LH/FSH), think Secondary (Panhypopituitarism). If they only have the "Big H's," think Primary.
