A 37-amino acid peptide derived from the calcitonin gene. It occurs as a result of alternative processing of mRNA from the calcitonin gene. The neuropeptide is widely distributed in the brain, gut, perivascular nerves, and other tissue. The peptide produces multiple biological effects and has both circulatory and neurotransmitter modes of action. In particular, it is a potent endogenous vasodilator.

Arg is replaced by Cys at position 18; a synthetic antigenic fragment.

Cpd is CGRP receptor antagonist, but is an agonist for calcitonin receptor.