Proopiomelanocortin (POMC) is converted into alpha-melanocyte-stimulating hormone (alpha-MSH), which acts centrally on the melanocortin receptor 4 (MC 4) to reduce dietary intake. Genetic defects in POMC production and mutations in the MC4 gene are described as monogenic causes of obesity in humans.

Of particular interest is the fact that patients with POMC mutations tend to have red hair because of the resultant deficiency in MSH production. Also, because of their diminished levels of adrenocorticotropic hormone (ACTH), they tend to have central adrenal insufficiency.

Data propose that up to 5% of children who are morbidly obese have MC4 or POMC mutations. If confirmed, these would be the most common identifiable genetic defects associated with obesity in humans (band 2p23 for POMC and band 18q21.3 for MC4).