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A. Structure

There are two forms : somatostatin 14 and somatostatin 28.


B. Site

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.

C. Actions:

1. Inhibits

  1. the secretion of gastrin, VIP, GIP, secretin, and motilin
  2. pancreatic exocrine secretion
  3. gastric acid secretion and motility
  4. gall bladder contraction
  5. the absorption of glucose, amino acids and triglycerides
  6. 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

2. Structure

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)


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