<p>Corticotropin-releasing factor (CRF) (corticoliberin) [<cite idref="PUB00004937"/>] is a hormone from the hypothalamus that regulates the release of corticotropin (ACTH) from the pituitary gland. CRF is evolutionary related to a number of other active peptides which are listed below.</p> <ul> <li>Urocortin (Ucn) [<cite idref="PUB00004223"/>], a brain mammalian peptide with corticotropin-releasing factor activity.</li> <li>Urotensin 1 from the urophysis of fish. Like CRF and Ucn, it acts in ACTH secretion.</li> <li>Sauvagine from frog skin, a peptide with a potent hypotensive action that elicits a diuretic effect.</li> <li>Diuretic hormone (DH) (or diuretic peptide (DP) from a variety of insects. DH is involved in the regulation of fluid secretion [<cite idref="PUB00004505"/>].</li> </ul><p>All these hormones are peptides of about 40 amino acid residues which are C-terminally amidated and processed from a larger precursor protein. This signature is a pattern of conserved residues, running from position 4 to 19 in these peptides.</p>