D cells produce somatostatin
Somatostatin is a hormone that inhibits the secretion of several other hormones, including growth hormone, thyroid stimulating hormone, cholecystokinin and insulin.
Alternative names for somatostatin
SS, SST or SOM; growth hormone inhibitory hormone (GHIH); somatotropin release inhibiting factor (SRIF); somatotropin release inhibiting hormone (SRIH).
What is somatostatin?
Somatostatin is a hormone produced by many tissues in the body, principally in the nervous and digestive systems. It regulates a wide variety of physiological functions and inhibits the secretion of other hormones, the activity of the gastrointestinal tract and the rapid reproduction of normal and tumour cells. Somatostatin may also act as a neurotransmitter in the nervous system.
The hypothalamus is a region of the brain that regulates secretion of hormones from the pituitary gland located below it. Somatostatin from the hypothalamus inhibits the pituitary gland’s secretion of growth hormone and thyroid stimulating hormone.
In addition, somatostatin is produced in the pancreas and inhibits the secretion of other pancreatic hormones such as insulin and glucagon. Somatostatin is also produced in the gastrointestinal tract where it acts locally to reduce gastric secretion, gastrointestinal motility and to inhibit the secretion of gastrointestinal hormones, including gastrin and secretin.
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.
How is somatostatin controlled?
In the same way that somatostatin controls the production of several hormones, these hormones feedback to control the production of somatostatin. This is increased by raised levels of these other hormones and reduced by low levels.
Somatostatin is also secreted by the pancreas in response to many factors related to food intake, such as high blood levels of glucose and amino acids.
What happens if I have too much somatostatin?
Excessive somatostatin levels in the bloodstream may be caused by a rare endocrine tumour that produces somatostatin, called a ‘somatostatinoma’. Too much somatostatin results in extreme reduction in secretion of many endocrine hormones. 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 and diarrhoea.
What happens if I have too little somatostatin?
Since somatostatin regulates many physiological processes, too little somatostatin production would lead to a variety of problems, including too much secretion of growth hormone. However, there are very few reports of somatostatin deficiency.