Pancreatic beta-cell stimulation tests in transient and persistent congenital hyperinsulinism

In congenital hyperinsulinism (HI), the in vivo pancreatic beta -cell funct ion is poorly described. Among 14 neonates with severe hyperinsulinaemic hy poglycaemia, 2 patients had very prolonged or persistent hypoglycaemia and mutation in the sulphonylurea receptor SUR1 gene. Patient I had transient H I and was treated medically for 3.5 mo before clinical remission was seen. He had initially very high basal and stimulated C-peptide and insulin level s, followed by a state of normal preprandial values, but blunted beta -cell glucose sensitivity, before complete beta -cell normalization occurred. A single, paternal SUR1 mutation, G1382S, was found suggesting focal type HI. Patient 2 had persistent HI and underwent 3 pancreas resections up to the age of 2 y, 7 mo, followed by a state of mild diabetes. On biopsy, diffuse- type beta -cell hypertrophy was seen. The beta -cell response to glucose an d glucagon stimulation was blunted before, as well as after, pancreas resec tions. Compound heterozygosity for the SUR I mutations 3992-3c to g and N18 8S was found. Conclusion: Transient, possibly focal, HI with paternal SUR1 mutation was a ssociated with a gradual, but complete normalization of the in vivo beta -c ell function; in the diffuse type HI, a blunted beta -cell response to gluc ose and glucagon stimulation persisted. In vivo beta -cell stimulation test s may contribute to the characterization of the HI subtypes.