Precursor protein of pituitary hormones that are involved in diverse physiological processes, including the regulation of energy balance, stress response, immune function and skin pigmentation. {ECO:0000269|PubMed:10403794, ECO:0000269|PubMed:8392067, ECO:0000269|PubMed:8396929, ECO:0000269|PubMed:8463333, ECO:0000269|PubMed:8636348, ECO:0000269|PubMed:9620771}. [Corticotropin]: Functions as a ligand for the melanocortin receptors MC1R, MC2R, MC3R and MC5R (PubMed:8396929, PubMed:8463333, PubMed:8636348). Activation of MC1R increases melanogenesis in melanocytes found in the skin and hair (PubMed:9620771). Binding to MC2R stimulates the adrenal glands to secrete cortisol (PubMed:8636348). Contributes to the regulation of energy homeostasis through activation of MC3R (Probable). Involved in the regulation exocrine gland function through MC5R activation (By similarity). {ECO:0000250|UniProtKB:P01193, ECO:0000269|PubMed:8396929, ECO:0000269|PubMed:8463333, ECO:0000269|PubMed:8636348, ECO:0000269|PubMed:9620771, ECO:0000305|PubMed:8463333}. [Melanocyte-stimulating hormone alpha]: Serves as a ligand for the melanocortin receptors MC1R, MC3R, MC4R and MC5R (PubMed:8392067, PubMed:8396929, PubMed:8463333). Activation of MC1R promotes melanogenesis in melanocytes of the skin and hair (PubMed:10403794, PubMed:9620771). Contributes to the regulation of energy homeostasis through activation of MC3R (Probable). Through MC4R activation, functions as an anorexigenic peptide (PubMed:8392067). Promotes immunosuppression and involved in the regulation exocrine gland function through MC5R activation (By similarity). {ECO:0000250|UniProtKB:P01193, ECO:0000269|PubMed:10403794, ECO:0000269|PubMed:8392067, ECO:0000269|PubMed:8396929, ECO:0000269|PubMed:8463333, ECO:0000269|PubMed:9620771, ECO:0000305|PubMed:8463333}. [Melanocyte-stimulating hormone beta]: Functions as a ligand for the melanocortin receptors MC1R, MC3R, MC4R and MC5R (PubMed:8396929, PubMed:8463333). Activation of MC1R increases melanogenesis in melanocytes found in the skin and hair (Probable). Contributes to the regulation of energy homeostasis through activation of MC3R (Probable). Through MC4R activation, functions as an anorexigenic peptide (PubMed:8392067). Involved in the regulation exocrine gland function through MC5R activation (By similarity). {ECO:0000250|UniProtKB:P01193, ECO:0000269|PubMed:8392067, ECO:0000269|PubMed:8396929, ECO:0000269|PubMed:8463333, ECO:0000305|PubMed:8463333}. [Melanotropin gamma]: Functions as a ligand for the melanocortin receptors MC1R, MC3R, MC4R and MC5R (PubMed:8396929, PubMed:8463333). Activation of MC1R increases melanogenesis in melanocytes found in the skin and hair (Probable). Contributes to the regulation of energy homeostasis through activation of MC3R (Probable). Binds to MC4R with low potency (PubMed:8392067). Involved in the regulation exocrine gland function through MC5R activation (By similarity). {ECO:0000250|UniProtKB:P01193, ECO:0000269|PubMed:8392067, ECO:0000269|PubMed:8396929, ECO:0000269|PubMed:8463333, ECO:0000305|PubMed:8463333}. [Beta-endorphin]: Endogenous orexigenic opiate. [Met-enkephalin]: Endogenous opiate. This is the function of Ensembl gene identifier ENSG00000115138 (POMC, proopiomelanocortin).