There are two forms : somatostatin 14 and somatostatin 28.
It is secreted by D cells in the islets of pancreas and by similar D cells in the GI mucosa. (Somatostatin, which is the growth hormone-inhibiting hormone was originally isolated from the hypothalamus).
Somatostatin is secreted more into the GI lumen than into the bloodstream; this is true of other GI hormones also.
- the secretion of gastrin, VIP, GIP, secretin, and motilin
- pancreatic exocrine secretion
- gastric acid secretion and motility
- gall bladder contraction
- the absorption of glucose, amino acids and triglycerides
- as mentioned under gastrin, acid inhibits gastrin secretion; one of the ways may be as follows :
Acid -> stimulates somatostatin secretion -> this in turn inhibits gastrin secretion Ghrelin
It is a polypeptide having 28 amino acids.
a. Site: It is secreted primarily from the stomach.
i. it may play an important role in the central control of food intake
ii. stimulates growth hormone secretion (by a direct action on the receptors in the pituitary)