Table 1.

Melanocortin receptor family: agonist affinity, antagonists, tissue distribution and main functions

MCR	Agonist affinity	Antagonists	Tissue expression	Main function
MC1R	α-MSH ≥ ACTH = β-MSH > γ-MSH	Agouti	Skin; immune cells; brain; pituitary; corpus luteum; placenta; testis; adipocytes	Pigmentation; anti-inflammatory
MC2R	ACTH	Agouti	Adrenal gland; skin; adipocytes	Adrenal steroidogenesis
MC3R	γ-MSH = α-MSH = ACTH > β-MSH	Agouti; AgRP	Brain; placenta; stomach; pancreas; duodenum; heart; testis; mammary gland; muscle cells; kidney; immune cells	Energy homeostasis; anti-inflammatory
MC4R	α-MSH ≥ ACTH > β-MSH > γ-MSH	Agouti; AgRP	Brain; sympathetic nervous system; muscles; adipocytes	Energy homeostasis
MC5R	α-MSH ≥ ACTH > β-MSH > γ-MSH	Agouti; AgRP	Exocrine glands; adrenal gland; pituitary; kidney; liver; lung; lymphatic system; testis; ovary; uterus; gastrointestinal tract; skin; skeletal muscle cells; adipocytes; B-lymphocytes; brain	Exocrine gland secretion; fatty acid β-oxidation; adipocyte lipid metabolism