Somatostatin also inhibits the secretion of TSH and that of virtually all of the glands of the pancreas and gastrointestinal tract, including glucagon, insulin, gastric acid, and intestinal enzymes (Fig. 1.20). Furthermore, it inhibits salt/water transport across the intestine. Somatostatin is present in almost every tissue, in nerve terminals and/or in specialised glandular cells on which it acts. It is widely distributed in tissues where it acts in some situations as a paracrine secretion (i.e. control of one cell by secretion of an adjacent cell), and in others as a neuroendocrine secretion (e.g. as in the tuberohypophysial neurones of the hypothalamus).
