Melanocyte-stimulating hormone
Summary
A peptide hormone (alpha-MSH, derived from POMC) that stimulates melanin production and darkens skin pigmentation. Also involved in appetite regulation and immune function.
Detail
Alpha-MSH is cleaved from POMC in the pituitary and hypothalamus. It acts on MC1R on melanocytes to increase melanin synthesis, causing skin darkening. Beyond pigmentation, MSH acts on MC3R/MC4R in the hypothalamus to suppress appetite and modulate immune responses. In Cushing syndrome or ectopic ACTH secretion, elevated ACTH/MSH drives hyperpigmentation. MC4R mutations cause monogenic obesity. The POMC pathway integrates neuroendocrine signals governing metabolism, reproduction, and immunity.
Sources
- First Aid for the USMLE Step 1
- Pathoma
- Harrison's Principles of Internal Medicine
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