biology

Somatostatin

Somatostatin is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Somatostatin rather than just read about it. In short: Somatostatin, also known as growth hormone-inhibiting hormone (GHIH) or by several other names, is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G protein-coupled somatostatin receptors and inhibition of the release of numerous secondary hormones. Somatostatin inhibits insulin and glucagon secretion.

Key takeaways

Somatostatin belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Somatostatin to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Somatostatin from memory before moving on to harder problems.

Reference excerpt

Somatostatin, also known as growth hormone-inhibiting hormone (GHIH) or by several other names, is a peptide hormone that regulates the endocrine system and affects neurotransmission and cell proliferation via interaction with G protein-coupled somatostatin receptors and inhibition of the release of numerous secondary hormones. Somatostatin inhibits insulin and glucagon secretion. Somatostatin has two active forms produced by the alternative cleavage of a single preproprotein: one consisting of 14 amino acids (shown in infobox to right), the other consisting of 28 amino acids. Alternate cleavage sites of the SST preproprotein results in the production of the hormone Neuronostatin, which has two active forms as Neuronostatin-13 and Neuronostatin-19. Neuronostatin is distinct from Somatostatin in its amino acid sequence, post-translation modifications and receptor binding. Among the vertebrates, there exist six different somatostatin genes that have been named: SS1, SS2, SS3, SS4, SS5 and SS6. Zebrafish have all six. The six different genes, along with the five different somatostatin receptors, allow somatostatin to possess a large range of functions. Humans have only one somatostatin gene, SST.

Nomenclature Synonyms of "somatostatin" include:

growth hormone–inhibiting hormone (GHIH) growth hormone release–inhibiting hormone (GHRIH) somatotropin release–inhibiting factor (SRIF) somatotropin release–inhibiting hormone (SRIH)

Production

Digestive system Somatostatin is secreted by delta cells at several locations in the digestive system, namely the pyloric antrum, the duodenum and the pancreatic islets. Somatostatin released in the pyloric antrum travels via the portal venous system to the heart, then enters the systemic circulation to reach the locations where it will exert its inhibitory effects. In addition, somatostatin release from delta cells can act in a paracrine manner. In the stomach, somatostatin acts directly on the acid-producing parietal cells via a G-protein coupled receptor (which inhibits adenylate cyclase, thus effectively antagonising the stimulatory effect of histamine) to reduce acid secretion. Somatostatin can also indirectly decrease stomach acid production by preventing the release of other hormones, including gastrin and histamine which effectively slows down the digestive process.

Brain

Somatostatin is produced by neuroendocrine neurons of the ventromedial nucleus of the hypothalamus. These neurons project to the median eminence, where somatostatin is released from neurosecretory nerve endings into the hypothalamohypophysial system through neuron axons. Somatostatin is then carried to the anterior pituitary gland, where it inhibits the secretion of growth hormone from somatotrope cells. The somatostatin neurons in the periventricular nucleus mediate negative feedback effects of growth hormone on its own release; the somatostatin neurons respond to high circulating concentrations of growth hormone and somatomedins by increasing the release of somatostatin, so reducing the rate of secretion of growth hormone. Somatostatin is also produced by several other populations that project centrally, i.e., to other areas of the brain, and somatostatin receptors are expressed at many different sites in the brain. In particular, populations of somatostatin neurons occur in the arcuate nucleus, the hippocampus, and the brainstem nucleus of the solitary tract.

Functions

Somatostatin is classified as an inhibitory hormone, and is induced by low pH. Its actions are spread to different parts of the body. Somatostatin release is inhibited by the vagus nerve.

Anterior pituitary In the anterior pituitary gland, the effects of somatostatin are:

Inhibiting the release of growth hormone (GH) (thus opposing the effects of growth hormone–releasing hormone (GHRH)) Inhibiting the release of thyroid-stimulating hormone (TSH) Inhibiting the release of prolactin (PRL)

Gastrointestinal system Somatostatin is homologous with cortistatin (see somatostatin family) and suppresses the release of gastrointestinal hormones Decreases the rate of gastric emptying, and reduces smooth muscle contractions and blood flow within the intestine Inhibits adenylyl cyclase in parietal cells, thereby suppressing gastric acid secretion Suppresses the release of pancreatic hormones Somatostatin release is triggered by the beta cell peptide urocortin3 (Ucn3) to inhibit insulin release. Inhibits the release of glucagon Suppresses the exocrine secretory action of the pancreas

Synthetic substitutes

Octreotide (brand name Sandostatin, Novartis Pharmaceuticals) is an octapeptide that mimics natural somatostatin pharmacologically, though is a more potent inhibitor of growth hormone, glucagon, and insulin than the natural hormone, and has a much longer half-life (about 90 minutes, compared to 2–3 minutes for somatostatin). Since it is absorbed poorly from the gut, it is administered parenterally (subcutaneously, intramuscularly, or intravenously). It is indicated for symptomatic treatment of carcinoid syndrome and acromegaly. It is also finding increased use in polycystic diseases of the liver and kidney. Lanreotide (Somatuline, Ipsen Pharmaceuticals) is a medication used in the management of acromegaly and symptoms caused by neuroendocrine tumors, most notably carcinoid syndrome. It is a long-acting analog of somatostatin, like octreotide. It is available in several countries, including the United Kingdom, Australia, and Canada, and was approved for sale in the United States by the Food and Drug Administration on August 30, 2007. Pasireotide, sold under the brand name Signifor, is an orphan drug approved in the United States and the European Union for the treatment of Cushing's disease in patients who fail or are ineligible for surgical therapy. It was developed by Novartis. Pasireotide is somatostatin analog with a 40-fold increased affinity to somatostatin receptor 5 compared to other somatostatin analogs.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Somatostatin

Start with the simplest possible case. Write down what Somatostatin claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Somatostatin before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Somatostatin ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Somatostatin

In research: Somatostatin appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Somatostatin in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Somatostatin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Antidiarrhoeals, Endocrine system, Genes on human chromosome 3, so understanding it makes those chapters shorter.
In everyday life: Look for Somatostatin outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Somatostatin in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Somatostatin means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Somatostatin out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Somatostatin in simple terms?

Why does Somatostatin matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Somatostatin?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Somatostatin.