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MBBS QUESTION #10293
Question 1
Addison's disease (primary adrenal insufficiency) classically presents with hyperpigmentation of the skin and mucous membranes. This finding is best explained by:
  • A direct stimulatory effect of low cortisol levels on melanocytes
  • Compensatory pituitary overproduction of ACTH (and its precursor POMC, which also yields melanocyte-stimulating hormone) due to loss of cortisol's negative feedback✔️
  • Excess aldosterone directly stimulating melanocytes
  • Chronic hyperglycemia causing pigment deposition in skin
Correct Answer Explanation
Loss of adrenal cortisol production removes negative feedback on the hypothalamic-pituitary axis, driving markedly increased ACTH secretion; since ACTH is cleaved from the larger POMC precursor that also yields melanocyte-stimulating hormone, chronically elevated POMC-derived peptides stimulate melanocytes, producing the characteristic hyperpigmentation of primary (but not secondary) adrenal insufficiency.