Suppression of primary and secondary peptides with somatostatin analog in the therapy of functional endocrine tumors.

Sandostatin (SMS 201-995 (SMS)), a potent, long acting analog of native somatostatin was used in five patients with functional endocrine tumors (gastrinoma, two patients; insulinoma, one patient; glucagonoma, one, and adult onset nesidioblastosis, one). Primary and secondary peptide levels were obtained during provocation with a test meal, a calcium infusion, a secretin bolus and either a glucagon or tolbutamide bolus. During provocation test, the levels of the primary peptides insulin and C-peptide (nesidioblastosis and insulinoma), gastrin (gastrinoma), glucagon (glucagonoma) and the secondary peptides calcitonin, gastrointestinal peptide, gastrin releasing peptide, motilin, neurotensin, pancreatic polypeptide, somatostatin, substance-P and vasoactive intestinal peptide were obtained at predetermined intervals and quantitated by radioimmunoassay. SMS therapy was begun and peptide levels were again obtained during provocation. SMS suppressed basal primary peptide levels in all patients by more than 50 per cent. In 23 of 26 provocative tests, SMS effectively decreased circulating peptide levels by more than 50 per cent. Thirteen instances of elevated basal secondary peptides were discovered, and SMS universally suppressed these levels by a mean of 54 per cent. Of the 44 provocative tests performed, elevated secondary peptide levels were present in 41. SMS was effective in 31 of these 41 tests. The mean suppression of these provoked secondary peptide levels was 70 per cent. SMS effectively suppresses both basal and provoked peptides and, thus, provides relief of the clinical symptoms induced by pathologic elevations of primary and secondary peptides.