The Case of the Insolent Insulin

    A patient was admitted to the emergency room of a hospital in insulin shock. Radioimmunoassay showed high levels of insulin in the blood. Physicians first suspected an insulinoma, a cancer of the pancreas that would cause it to over-secrete insulin. However, the biopsy was negative, and the patient was released. Several weeks later, the patient again showed up in insulin shock. This time, the lab adjusted the RIA to detect preproinsulin as well as insulin. The patient tested positive for insulin as before, and tested negative for preproinsulin.