The clinical symptoms that may be associated with medullary carcinoma of the thyroid are summarised in Figs. 16.20.
The diarrhoea is severe and watery due to a combination of intestinal hurry and excessive secretion. It is relieved by removal of the tumour and recurs with metastases. The cause of the secretion has not been identified but calcitonin, a bradykinin-producing kallikrein, prostaglandins, and vasoactive intestinal peptide have all been implicated. The peptide hormones that have been identified in tumour tissue and in the blood are also listed in Fig. 16.20. The basal level of calcitonin is high and rises greatly after a provocative infusion of ionised calcium or following the oral administration of alcohol or pentagastrin.
