Somatotropin release-inhibiting hormone

Growth hormone-releasing hormone (GHRH) (+) Somatotropin release-inhibiting hormone (SRIH, somatostatin) (-) Growth hormone (somatotropin, GH) Liver Insulin-like growth factors (IGF, somatomedins)... 

Somatotropin release inhibiting hormone (SIH), somatostatin a polypeptide, M, 1638, which inhibits secretion of somatotropin, thyrotropin, insulin, glucagon, gastrin and cholecystokinin. SIH has a broad activity spectrum it acts outside the hypothalamus as a neurotransmitter in the central nervous system, and as a hormone in the intestinal tract it has also been found in the thyroid and pancreas. 

SIH acronym of Somatotropin release inhibiting hormone. See Releasing hormones. 

Somatostatin (or somatotropin release-inhibiting factor [SRIF]) occurs primarily as a 14-amino acid peptide, although a 28-amino acid form also exists. As with the other hypothalamic peptides, it is formed by proteolytic cleavage of a larger precursor. Somatostatin, originally isolated from the hypothalamus, is also in many other locations, including the cerebral cortex, brainstem, spinal cord, gut, urinary system, and skin. Somatostatin inhibits the secretion of many substances in addition to growth hormone (Table 59.1). 

Statins, release inhibiting factors, release inhibiting hormones, neurohormones synthesized in the small-cell region of the hypothalamus and transported via the bloodstream to the anterior pituitary. Members of the statins include melanostatin, somatostatin, and prolactostatin. They inhibit the secretion of melanotropin, somatotropin, and prolactin, respectively. Together with the corresponding liberins, the statins regulate the levels of the three pituitary hormones. 

Somatostatin [somatotropin release inhibiting factor (SRIF), Ala-Gly-cyclo(Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys)] is a hypothalamic hormone that inhibits the release of growth hormone, insulin, and glucagon. Somatostatin is believed to adopt an overall p-sheet conformation with a... 

Somatostatin SOM SST14 SST28 Somatotropin release inhibitory factor (SRIF) Growth hormone release-inhibiting factor... 

Opioid analgesics stimulate the release of ADH, prolactin, and somatotropin but inhibit the release of luteinizing hormone. These effects suggest that endogenous opioid peptides, through effects in the hypothalamus, regulate these systems (Table 31-1). 

Preprosomatostatin, a 116-amino acid peptide, is encoded on the long arm of chromosome 3. Somatostatin (SS-14), a cyclic peptide with a molecular weight of 1,600, is produced from the 14 amino acids at the C-terminus of this precursor molecule. SS-14 was first isolated from the hypothalamus and named for its ability to inhibit the release of growth hormone (GH, somatotropin) from the anterior pituitary. It also inhibits the release of insulin. In addition to the hypothalamus, somatostatin is also secreted from the D cells (8 cells) of the pancreatic islets, many areas of the central nervous system outside of the hypothalamus, and in gastric and duodenal mucosal cells. SS-14 predominates in the central nervous system (CNS) and is the sole form secreted by the 8 cells of the pancreas. In the gut, however, prosomatostatin (SS-28), which has 14 additional amino acids extending from the C-terminal portion of the precursor, makes up 70 to 75% of the immunoreactivity (the amount of hormone that reacts with antibodies to SS-14). The prohormone SS-28 is 7 to 10 times more potent in inhibiting the release of GH and insulin than is SS-14. 

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