Somatostatin Receptors as Markers for Endocrine Tumors

Endocrine tumors of the gastrointestinal tract are relatively rare neoplasias that secrete large amounts of peptide hormones such as insulin, glucagon, gastrin, or vasoactive intestinal peptide (VIP). 1 These substances are usually responsible for the distinct clinical features observed in patients with such tumors, named specifically insulinomas, glucagonomas, gastrinomas, VIPomas, or carcinoids. Although most are relatively slow-growing tumors, they may lead in early stages to dramatic symptoms such as hypoglycemia, gastric ulcerations, or watery diarrhea. Unfortunately, they are often difficult to localize precisely at that stage. 2 Somatostatin, 3 a tetradecapeptide that inhibits peptide hormone release in various sites such as the pituitary, the pancreas, and the gastrointestinal tract, has been shown recently to have beneficial effects when given chronically in the form of a stable non-degradable octapeptide analogue (SMS 201-995) in such gastrointestinal endocrine tumors. 4,5 It is likely that its therapeutic effect is due in part to inhibition