This maturation defect is linked to a deficiency in the proconvertase 1/3 enzyme (PC1/3) and at least partially explains the endocrine abnormalities of PWS, particularly obesity with hyperphagia due to a defect in the maturation of proopiomelanocortin (POMC), other pituitary hormone deficits, and problems with insulin, OT, and ghrelin maturation (37). The gene discussed is POMC; the disease is obesity due to melanocortin 4 receptor deficiency.