Which endocrine disorder is associated with hyperpigmentation of the skin?

• A. Cushing's syndrome
• B. Graves disease
• C. Hypothyroidism
• D. Addison's disease

Answer: (D)

Hyperpigmentation occurs when there’s primary adrenal failure, because the reduced cortisol triggers the pituitary to release more ACTH. ACTH is produced from the same precursor as melanocyte-stimulating hormone, so the excess ACTH also increases melanin production. The result is bronze-colored skin that can appear in sun-exposed areas and in skin creases, as well as on mucous membranes.

This pattern is characteristic of Addison's disease, where low cortisol and aldosterone from adrenal destruction lead to elevated ACTH. Other endocrine disorders like Cushing's syndrome, Graves disease, or hypothyroidism don’t produce this diffuse hyperpigmentation in the same way, though they have their own distinctive skin or systemic signs.