[Gastrointestinal hormone profile in medullary thyroid carcinoma]

Medullary thyroid carcinoma (MTC) can be important for gastroenterologists because 20-30% of patients with MTC suffer from chronic diarrhea and the tumor is capable of producing--besides other bioactive substances--a multitude of gastroenteropancreatic hormones. Gastrointestinal hormone profiles of 5 patients with MTC were determined both basally and after intravenous stimulation with secretin and calcium respectively. Diagnosis of MTC was confirmed histologically or cytologically and by demonstration of elevated serum concentration of calcitonin both basally and after calcium stimulation. 4/5 patients had chronic diarrhea. Normal values or only borderline increases were found for the following hormones: vasoactive intestinal polypeptide (VIP), neurotensin, substance P, growth hormone releasing hormone (GRH), glucagon, neurokinin A, peptide YY, and pancreatic polypeptide. Somatostatin was elevated after calcium stimulation in 1/5 patients only. The main findings were increased basal concentrations for GAWK in 5/5 patients and elevated concentrations for gastrin-releasing peptide (GRP, human bombesin) after calcium stimulation in 4/5. Probably as a consequence of the GRP increase, an increase in gastrin occurred in parallel, indicating bioactivity of the GRP released from the tumor. Besides calcitonin as the main tumor marker for MTC, determination of GAWK and GRP seems to provide helpful additional markers in laboratory diagnosis of MTC. GRP determination after i.v. calcium infusion allowed identification of patients with normal basal plasma GRP concentration.