History and clinical findings: For 15 months a 52-year-old business man had been suffering from chronic diarrhoea which had persisted even after exophthalmic hyperthyroidism (Grave's disease) had been diagnosed and adequately treated. Physical examination on admission revealed no abnormalities, in particular no sign of hyperthyroidism.
Investigations and diagnosis: Repeated stool examinations failed to demonstrate any infectious organisms. Upper gastrointestinal endoscopy and ileaocoloscopy were normal, as were biopsies. Persistence of the diarrhoea during a fasting test and the bulky stools suggested a secretory cause. Among various hormonal tests the calcitonin concentration was found to be greatly raised (4572 ng/l, normal 10 < ng/l). Ultrasound demonstrated a thyroid tumour and cytological examination of a fine-needle biopsy revealed a medullary carcinoma.
Treatment and course: After total thyroidectomy with bilateral neck dissection the patient was free of any symptoms: the diarrhoea ceased immediately after the operation and the calcitonin concentration became nearly normal.
Conclusions: Signs of chronic secretory diarrhoea suggest the possibility of an endocrinally active tumour. Search for a medullary carcinoma of the thyroid with measurement of the serum calcitonin level should be among the diagnostic procedures.