Somatostatin is a cyclic polypeptide hormone produced by various tissues in our body, mostly in the nervous and digestive systems. This growth hormone inhibitory hormone affects several areas of the body by hindering the secretion of other hormones. The main role of somatostatin is to prevent or hinder the production of other hormones and stop the unnatural rapid reproduction of cells. Two active forms of this peptide exist, fourteen amino acids Somatostatin and twenty-eight amino acids Somatostatin. 14 amino acids type works primarily in the brain, while 28 amino acids type operates in the Gastrointestinal tract. Its half-life is between 1 to 3 minutes.
somatostatin is also known as SS, SST or SOM; growth hormone inhibitory hormone (GHIH); somatotropin release inhibiting factor (SRIF); somatotropin release inhibiting hormone (SRIH).
somatostatin plays a major role in the activity of the gastrointestinal tract and the rapid reproduction of normal and tumour cells. It is known to inhibit GI, endocrine, exocrine, pancreatic, and pituitary secretions, as well as modify neurotransmission and memory formation in the CNS. Somatostatin can also act as a neurotransmitter in the nervous system.
Somatostatin inhibits the secretion of several gastrointestinal hormones—including gastrin, secretin, cholecystokinin (CCK), and vasoactive intestinal polypeptide (VIP)—resulting in the inhibition of many functions of the gastrointestinal tract, including secretion of acid by the stomach, secretion of digestive enzymes by the pancreas, and absorption of nutrients by the intestine.
somatostatin also provides indirect inhibition to cell growth by suppressing insulin-like growth factor I (IGF-1) and growth hormone which limits cells ability to thrive and survive. Somatostatin from the hypothalamus inhibits the pituitary gland’s secretion of thyroid stimulating hormone and in pancreas it also blocks the secretion of glucagon and insulin, these inhibitory procedures are the reason why it was named somatostatin meaning stagnation and calmness of the body.
Insulin, glucagon, and somatostatin act together to control the flow of nutrients into and out of the circulation. The relative concentrations of these hormones regulate the rates of absorption, utilization, and storage of glucose, amino acids, and fatty acids.
Chemically altered equivalents of somatostatin are used as a medical therapy to control too much hormone secretion in patients with acromegaly and other endocrine conditions, and to treat some gastrointestinal diseases and a variety of tumours.
note that Somatotropin is growth hormone that controls all the growth functions of the body. Whereas Somatostatin acts as the inhibitor of growth hormone and has the opposite effect so do not use these words interchangeably.
In the same way that somatostatin controls the production of several hormones, these hormones feed back to control the production of somatostatin. This is increased by raised levels of these other hormones and reduced by low levels.
Because it is an inhibitor, somatostatin is important to balance hormone levels in the body and stop the effects of over-production of certain hormones. That means that somatostatin levels that are too low can cause the problems associated with high levels of other hormones. Growth hormone, in particular, can be problematic. However, this is a rarely reported condition.
Instead, some patients will struggle with excessive somatostatin levels when they have a specific type of endocrine tumour called a somatostatinoma. This tumour produces the hormone independently. The end result is extreme suppression of the hormones normally inhibited by somatostatin, An example of this is suppression of insulin secretion from the pancreas leading to raised blood glucose levels (diabetes). As somatostatin inhibits many functions of the gastrointestinal tract, its overproduction may also result in the formation of gallstones, intolerance to fat in the diet, diarrhoea, abdominal cramps and pain, high blood glucose concentrations, weight loss, and episodic flushing of the skin.