Diarrhea and medullary carcinoma of the thyroid.

The authors present the case of a 34-year-old woman with disseminated medullary carcinoma of the thyroid to emphasize the value of calcitonin assay in the diagnosis of this condition despite the absence of a thyroid mass and negative scans. An increased concentration of serum carcino-embryonic antigen was confirmed. The diarrhea associated with the disease did not respond to indomethacin in this patient suggesting that in some cases of medullary carcinoma diarrhea is not due to excessive production of prostaglandins.