Successful therapy with calcium channel blocker (nifedipine) in persistentneonatal hyperinsulinemic hypoglycemia of infancy

appropriate management of persistent hyperinsulinemic hypoglycemia of infan cy (PHHI) still remains controversial. Some patients show a response to tre atment with diazoxide or somatostatin, but a number of children require tot al or near-total pancreatectomy to control hyperinsulinism. Recent studies suggest a dysfunction in the adenosine triphosphate-sensitive potassium cha nnel present in the plasma membrane of pancreatic beta-cells in PHHI. The c losure of these channels initiating the depolarization of the P-cen membran e and opening of calcium channels results in an increase in intracellular c alcium which triggers insulin secretion. A calcium channel blocking agent h as been shown to block this process and decrease insulin secretion of the n esidioblastotic beta-cells in vitro and to control the hyperinsulinemic hyp oglycemia of the patient in vivo. To examine the efficacy of calcium channe l blocker therapy, three patients with PHHI were treated with nifedipine. P HHI was diagnosed by inappropriately high insulin levels for low blood gluc ose levels at 8-10 days of age. Normoglycemia was maintained by a high dose of glucose infusion at a rate of 14-16 mg/kg/min. Therapy using diazoxide and/or somatostatin analogue failed to restore euglycemia in these three pa tients, The first patient underwent near-total pancreatectomy; however, hyp erinsulinism recurred 30 days after surgery. All patients were started on s hort acting nifedipine at a dose of 0.3 mg/kg/day per os in four doses. To maintain blood glucose levels in normal ranges, the dose of nifedipine was progressively increased to 0.7-0.8 mg/kg/day, Glucose infusion rate to rest ore euglycemia decreased and was discontinued on the 4(th) to 10(th) day of nifedipine treatment. The patients, who have now been followed on nifedipi ne therapy for over 12 months, are normoglycemic with normal insulin levels . The growth and neuromotor development of the patients are unremarkable ex cept for mild developmental delay of the patient who underwent near-total p ancreatectomy, No side effects were:encountered at the doses used. In concl usion, calcium channel blocking agents can be used with efficacy and safety in PHHI to control the hyperinsulinemia.