Adrenomedullin, a hypotensive peptide found in human pheochromocytoma, consists of 52 amino acids, has 1 intramolecular disulfide bond, and shows a slight homology with the calcitonin gene-related peptide. It may function as a hormone in circulation control because it is found in blood in a considerable concentration. The precursor, called preproadrenomedullin, is 185 amino acids long. By RNA-blot analysis, human adrenomedullin mRNA was found to be highly expressed in several tissues.