The Secretin family is a small family of 15 GPCRs (GPCR-B1) that all have an extracellular hormone-binding domain and bind peptide hormones. The members of this family are the calcitonin and calcitonin-like receptors (CALCR, CALCRL); the corticotropin-releasing hormone receptors (CRHR1, CRHR2); the glucagon receptor (GCGR); the gastric inhibitory polypeptide receptor (GIPR); the glucagon-like peptide receptors (GLP1R, GLP2R); the growth-hormone-releasing hormone receptor (GHRHR); the adenylate cyclase activating polypeptide receptor (PAC1/ADCYAP1R1); the parathyroid hormone receptors (PTHR1, PTHR2); the secretin receptor (SCTR); and the vasoactive intestinal peptide receptors (VIPR1, VIPR2).
The calcitonin gene-related peptide (CGRP) is an alternative product of the calcitonin gene and was first described in 1982. It is a potent vasodilator with multiple reported pharmacological activities (e.g. treatment of migraine).
 CGRP receptors: a headache to study, but will antagonists prove therapeutic in migraine? S.D. Brain, D.R. Poyner, R.G. Hill. Trends Pharmacol Sci, 2002, 23, 51-53