vasoactive-intestinal-peptide and Malignant-Carcinoid-Syndrome

Somatostatin is a peptide synthesized in many tissues that can act as a neurotransmitter, a systemic hormone, or a local hormone, and inhibits the secretion of hormones or other cell products. A long-acting synthetic analogue of somatostatin (SMS 201-995) has been developed which when administered subcutaneously has a biologic half-life of 90 to 120 minutes and can be administered 2 or 3 times per day. SMS 201-995 can lower plasma concentrations of growth hormone and somatomedin-C in patients with pituitary acromegaly, but no controlled trials to assess symptomatic response or change in tumor size have been done. In patients with pituitary thyrotropin-producing pituitary tumors, SMS 201-995 has been remarkably effective in producing biochemical and clinical responses and is the drug of first choice in this syndrome when tumor resection is not possible. In patients with the carcinoid syndrome, SMS 201-995 effectively reduces diarrhea, is the best available drug for treatment of carcinoid flush (effective in approximately 90% of cases), and is useful in treating carcinoid crisis. Eighty-five percent of patients with pancreatic islet cell tumors that produce vasoactive intestinal peptide will respond to SMS 201-995 with a reduction in diarrhea that often has been resistant to all other therapy. SMS 201-995 may also be useful in treating the symptoms in some patients with glucagonomas, growth hormone releasing hormone-producing tumors and insulinomas. Whether SMS 201-995 has a significant effect on gut neuroendocrine tumor growth remains uncertain. Certain nonmalignant diseases of the gut respond to somatostatin, including secretory diarrhea and fistulas of unknown cause. In general, SMS 201-995 has proved safe with few significant side effects, but whether the long-term use of the drug will result in an iatrogenic form of the somatostatinoma syndrome is uncertain.

Topics: Acromegaly; Adenoma, Islet Cell; Diarrhea; Gastrointestinal Diseases; Gastrointestinal Hemorrhage; Gastrointestinal Neoplasms; Growth Hormone; Humans; Intestinal Fistula; Malignant Carcinoid Syndrome; Octreotide; Pancreatic Neoplasms; Pancreatitis; Pituitary Neoplasms; Thyrotropin; Vasoactive Intestinal Peptide

Previous studies showed increased plasma motilin and substance P concentrations and accelerated motor function in the small bowel and colon in patients with carcinoid diarrhea. Octreotide is beneficial in patients with carcinoid syndrome. Our hypothesis was that octreotide inhibits accelerated motility and gut neuropeptides in carcinoid syndrome.. In 12 patients with metastatic carcinoid syndrome, we investigated the effect of octreotide 50 microg s.c. t.i.d (n = 6) or placebo (n = 6) on postprandial symptoms, GI transit, colonic motility, and circulating levels of selected circulating peptides and amines.. Octreotide reduced postprandial flushing (p = 0.03) but not pain. Octreotide significantly retarded overall colonic transit and proximal colonic emptying (p < 0.05); it tended to prolong small bowel transit time (p = 0.13) and to reduce postprandial colonic tone (p = 0.08) compared with placebo. Octreotide also reduced circulating levels of peptide YY, neurotensin, vasoactive intestinal polypeptide, and substance P but had no effect on plasma motilin, neuropeptide Y, calcitonin gene-related peptide, or histamine after meal ingestion.. Octreotide ameliorates gut motor dysfunctions that characterize carcinoid diarrhea; the potential role of specific antagonism of serotonin, substance P, and vasoactive intestinal polypeptide alone or in combination with agents that inhibit their release in carcinoid diarrhea deserves further study.

Topics: Aged; Antineoplastic Agents, Hormonal; Calcitonin Gene-Related Peptide; Colon; Colonic Diseases; Diarrhea; Digestion; Double-Blind Method; Female; Flushing; Gastrointestinal Agents; Gastrointestinal Motility; Gastrointestinal Transit; Histamine; Humans; Intestine, Small; Male; Malignant Carcinoid Syndrome; Middle Aged; Motilin; Neuropeptide Y; Neuropeptides; Neurotensin; Octreotide; Peptide YY; Placebos; Serotonin Antagonists; Substance P; Vasoactive Intestinal Peptide

Topics: Achlorhydria; APUD Cells; Apudoma; Carcinoid Tumor; Carcinoma; Cholecystokinin; Diarrhea; Endocrine System Diseases; Humans; Hypokalemia; Malignant Carcinoid Syndrome; Neoplasms; Pancreatic Diseases; Paraganglioma; Paraneoplastic Endocrine Syndromes; Peptides; Prostaglandins E; Somatostatin; Syndrome; Thyroid Neoplasms; Vasoactive Intestinal Peptide