Table 1.

A summary of the primary function, ligand and site of expression of the melanocortin receptors. (^* Indicates primary ligand.)

receptor	potency of ligand activation	principal site of expression	principal function
MC1-R	α-MSH = ACTH > β-MSH > γ-MSH	melanocytes	pigmentation
MC2-R	ACTH	adrenal gland	steroidogenesis
MC3-R	α-MSH = ACTH =β-MSH =γ-MSH*	brain	energy homeostasis, natriuresis
MC4-R	α-MSH = ACTH > β-MSH > γ-MSH	brain	energy homeostasis
MC5-R	α-MSH > ACTH* > β-MSH > γ-MSH	exocrine glands	exocrine gland secretion