The diagnosis of an insulin-secreting islet cell adenoma was obscured in a patient treated with diphenylhydantoin sodium. Comparison of insulin responses to glucagon, tolbutamide, and leucine before and after drug withdrawal indicated that the diphenylhydantoin was inhibiting "stimulated" insulin release from the tumor. Another clue to hyperinsulinism was the restraint of hepatic ketogenesis and urinary nitrogen excretion during fasting. Diphenylhydantoin, or an analogue, may deserve further trial as adjunctive therapy in the control of insulinoma-induced hypoglycemia.
Robert H. Knopp, James C. Sheinin, Norbert Freinkel. Diphenylhydantoin and an Insulin-Secreting Islet Adenoma. Arch Intern Med. 1972;130(6):904–908. doi:10.1001/archinte.1972.03650060094017