Somatostatin

Sst, ISH, E15.5, telencephalon

Sst, ISH, p56 mouse

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Somatostatin, also known as growth hormone-inhibiting hormone (GHIH), is a peptide hormone that plays a crucial role in the human body by inhibiting the secretion of several other hormones. It is produced by various tissues, including the hypothalamus, pancreas, and the digestive system. Somatostatin has a wide range of effects and is involved in the regulation of the endocrine system and nervous system, as well as in cell proliferation.

Production and Structure

Somatostatin is synthesized in the body as a preprohormone, which is then cleaved to produce a prohormone. This prohormone is further cleaved to generate two active forms of somatostatin: one consisting of 14 amino acids (somatostatin-14) and the other of 28 amino acids (somatostatin-28). The distribution of these forms varies, with somatostatin-14 being more prevalent in the central nervous system (CNS), and somatostatin-28 being more common in the gastrointestinal tract.

Functions

The primary function of somatostatin is to inhibit the release of growth hormone (GH) from the anterior pituitary gland, thereby playing a key role in regulating body growth and metabolism. In addition, it suppresses the secretion of thyroid-stimulating hormone (TSH) from the pituitary gland, which affects thyroid gland function.

In the pancreas, somatostatin inhibits the secretion of both insulin and glucagon, which are crucial for blood glucose regulation. It also reduces the release of other hormones and enzymes involved in the digestive process, making it an important regulator of the digestive system.

Furthermore, somatostatin acts as a neurotransmitter and neuromodulator in the CNS, influencing various neurological functions.

Clinical Significance

Somatostatin analogs, such as octreotide and lanreotide, have been developed for medical use. These synthetic forms of somatostatin have longer half-lives and are used to treat a variety of conditions, including acromegaly, a disorder characterized by excessive growth hormone production, and certain types of tumors that secrete hormones, such as neuroendocrine tumors.

Somatostatin and its analogs are also used in the management of gastrointestinal bleeding and for the treatment of severe diarrhea associated with specific conditions, such as HIV/AIDS and chemotherapy.

Receptors

Somatostatin exerts its effects through binding to specific G protein-coupled receptors (GPCRs) on the surface of target cells. There are five known somatostatin receptors (SSTR1-5), which are differentially expressed in various tissues. The wide distribution of these receptors contributes to the diverse effects of somatostatin in the body.

Conclusion

Somatostatin is a multifunctional hormone that plays a vital role in the regulation of growth, metabolism, and various bodily functions. Its ability to inhibit the secretion of several hormones makes it an important target for therapeutic interventions in a range of diseases and conditions.