Somatostatin: The Peptide Hormone That Switches Others Off, Its Five Receptors and the Medicines Built on It

Somatostatin is a peptide hormone that switches other hormones off. MeSH, the U.S. National Library of Medicine's subject index, describes it as a 14-amino-acid peptide named for its ability to inhibit the release of growth hormone from the pituitary, which is why it is also called somatotropin release-inhibiting factor (SRIF). It is made in the brain, the nerves, the gut, the pancreas and other organs.

It holds back the release of other hormones. UniProt records that it inhibits the secretion of several pituitary hormones, including growth hormone, prolactin, ACTH, luteinizing hormone and TSH. MeSH adds insulin and glucagon from the pancreas, and records that the D cells of the gut and pancreas use it to hold back gastrin, insulin and renin, acting on nearby cells as well as through the blood. In the brain it also works as a neurotransmitter and neuromodulator.

In several places. It is released by the hypothalamus, where it brakes growth hormone release from the pituitary, and by the D cells (delta cells) of the pancreatic islets and the gut. MeSH also records it throughout the central and peripheral nervous systems.

Both are cut from the same precursor of 116 amino acids. Somatostatin-28 is the longer form; somatostatin-14 is its last 14 amino acids, AGCKNFFWKTFTSC, closed into a ring by a disulfide bond between its two cysteines. MeSH records that somatostatin-28 has the same biological activities with a 14-amino-acid extension at the front, and that it is the main form in the gut.

Five receptors, SSTR1 to SSTR5, each a G protein-coupled receptor that, UniProt records, inhibits the enzyme adenylyl cyclase when activated. They differ in which form of the hormone they prefer and where they are found: SSTR2 is the dominant one on the insulin- and glucagon-making cells of the pancreas, and SSTR5 prefers somatostatin-28. Many neuroendocrine tumours carry these receptors, which is what the imaging agents and Lutathera are built to find.

Shorter, longer-lasting peptides built to act like somatostatin. U.S. labels describe octreotide as a cyclic octapeptide with actions mimicking the natural hormone, lanreotide as a synthetic cyclical octapeptide analogue, and pasireotide as a cyclohexapeptide that mimics it. They are approved as medicines for conditions such as acromegaly, certain hormone-secreting tumours and Cushing's disease.

No. Octreotide is a synthetic analogue of eight amino acids; somatostatin-14 has fourteen. Octreotide keeps the Phe-Trp-Lys-Thr stretch from the middle of somatostatin-14, with tryptophan in its mirror-image D form, inside a smaller disulfide ring. The Sandostatin label calls it a long-acting octapeptide with actions that mimic the natural hormone. Drugs@FDA holds records for octreotide since 1988; a search by active ingredient on 5 November 2026 found none for somatostatin itself as a medicine.

A tumour that makes somatostatin. MeSH describes it as a somatostatin-secreting tumour derived from the delta cells of the pancreas, also found in the intestine, and associated with diabetes, gallstones, fatty stools and low stomach acid. This page does not discuss diagnosis or treatment; those belong with a clinician.

No. This page explains what somatostatin is, from public scientific and regulatory sources. It gives no dose, schedule or recommendation; anyone treated with these medicines should follow their own clinician and product label. Peptides sold for research are labelled research use only, not for human use. Medibact supplies USP-grade bacteriostatic water, made in the USA, and is not affiliated with any manufacturer of the products named here.