1. Calcitonin is a 32-membered heterodetic cyclic peptide comprising the sequence Cys-Ser-Asn-Leu-Ser-Thr-Cys-Val-Leu-Gly-Lys-Leu-Ser-Gln-Glu-Leu-His-Lys-Leu-Gln-Thr-Tyr-Pro-Arg-Thr-Asn-Thr-Gly-Ser-Gly-Thr-Pro-NH2 cyclised by a disulfide bridge between the two Cys residues at positions 1 and 7.It has a role as a metabolite and a bone density conservation agent.