Loss‐of‐function variants in genes in the leptin–melanocortin pathway, including LEP, LEPR, POMC, PCSK1, NCOA1 (associated with steroid receptor coactivator 1 deficiency), SH2B1, and SIM1, may result in monogenic MC4R pathway diseases and cause hyperphagia and early‐onset obesity [2, 3, 4, 52]. The gene discussed is NCOA1; the disease is hyperinsulinemic hypoglycemia, familial, 4.