Somatostatin, also called growth hormone release-inhibiting factor, is made as a 116 aa precursor that is cleaved in 3 chains: somatostatin-28 (SST-28), somatostatin-14 (SST-14)and neuronostatin (NST). Somatostatin inhibits the secretion of somatotropin. SST-14 corresponds to aa103-116 of precursor and inhibits the secretion of pituitary hormones. NST corresponds to aa 31-43 of the precursor and regulates arterial pressure. SST-28 corresponds to aa89-116 of precursor.