About Somatostatin Pituitary hormone, Growth inhibitor. Mechanism of Action of Somatostatin The drug exerts it`s action by inhibiting the secretion of Growth hormone (GH), Thyroid stimulating hormone (TSH), Prolactin in pituitary- Insulin and glucagons in pancreas, and all gastrointestinal secretions including gastrin and HCl. It constricts splanchnic, hepatic, and renal blood vessels. It decreases blood flow to gastrointestinal mucosa and thus controls bleeding esophageal varices and bleeding peptic ulcer. It controls pancreatic, intestinal, or biliary fistulae due to antisecretory effect