[Glucagon-producing carcinoid of the rectum--report of a case].

: A 22-year-old male who had been receiving insulin therapy to treat uncontrollable hyperglycemia, was diagnosed to have a carcinoid in the lower rectum. The excised tumor was 1.5 cm in diameter, and showed a yellowish-white cut surface. It did not invade into the proper muscle. Numerous glucagon immunoreactive cells were found. The tumor cells contained many rounded neurosecretory granules. After tumor excision, the patient's hyperglycemia did not return in the absence of insulin administration. We suggest that the tumor may have secreted glucagon which may have acted as an antagonist against insulin in the circulation.