Medical treatment of insulinomas: The role of diphenylhydantoin

Abstract

Surgical removal of the insulinoma continues to be the treatment of choice. Medical therapy should be considered in patients who cannot undergo surgery. We are reporting our experience with regard to the efficacy of Diphenylhydantoin (DPH) in controlling hypoglycemia and suppressing insulin release in patients with insulinomas. DPH was administered orally at a dose of 300–400mg/day to three patients with documented endogenous insulin excess. The first two patients received the drug temporarily during the preoperative period, with resolution of the hypoglycemic attacks, normalization of blood glucose, and reduction of insulin levels. Subsequent surgery confirmed the presence of insulin-secreting pancreatic tumor. Cure was achieved after excision of the tumor. The third patient represented a diagnostic and threrapeutic challenge. An insulin-secreting tumor located in the body of the pancreas was diagnosed in a patient with type 2 diabetes and end stage renal disease. The patient’s poor cardiac function contraindicated surgery. DPH resulted in an excellent sustained control of his blood sugar and a fall in insulin levels for several months. We believe that DPH is a potent inhibitor of insulin secretion and, thus, is suitable as a temporary therapeutic measure in the preoperative period of patients with insulinoma, as well as an alternative to surgery for those who are not surgical candidates.