Somatostatin receptors are activated by somatostatin secreted from nerve and endocrine cells. The Somatostatin Receptors (SSTRs) are expressed in a tissue-specific manner and involved in the regulation of secretion of insulin, glucagon and growth hormone as well as cell growth induced by neuronal excitation in both the central and peripheral nervous systems. Aberrant expression of somatostatin receptors is known in a large number of human tumors. The human medullary thyroid carcinoma cell line TT expresses all SSTR subtypes. SST5 is expressed in adult pituitary gland, heart, small intestine, adrenal gland, cerebellum and fetal hypothalamus. Expression has not been detected in fetal or adult kidney, liver, pancreas, uterus, spleen, lung, thyroid or ovary. SST5 is a candidate gene for bipolar affective disorder (BPAD) as well as for other neuropsychiatric disorders. Expression of SST2 and SST5 may be important in the growth inhibitory effect of somatostatin in human pancreatic cancer.