[The changes of insulin secretion in type A insulin resistance syndrome: a 7-year follow up]

A previously reported female diagnosed with type A insulin resistance syndrome bearing a heterozygous missense mutation of R1174W in the insulin receptor gene was followed for 7 years since the age of 16 years.

Five-hour oral glucose tolerance tests (OGTT) were done on baseline, the 3(rd), 6(th) and 7(th) year respectively, with serum insulin and C-peptide measured at the same time points. Areas under of curve (AUC) of glucose, insulin and C-peptide were compared between the years. Acute insulin response (AIR) was determined at baseline and the 7(th) year. The dose response were insulin secretion rates at each time point during OGTT being plotted over the corresponding glucose levels, and the slopes of which quantified the insulin secretion responding to glucose.

The follow up data showed that the glucose metabolism of the subject did not deteriorate over time with yearly glycosylated hemoglobin A1c (HbA1c) being normal (4.6% - 5.5%), and hyperinsulinemic hypoglycemia was a persistent phenomenon observed at 4 - 5 hours post-load. The fasting and AUCs of serum insulin and C-peptide tended to decline without simultaneously increase of those of plasma glucose. The AIR decreased by 56% as compared to baseline. The dose response curves shifted downward as years went by.

It supports that with the alleviation of physiological insulin resistance after puberty, the gross hyperinsulinemia tends to ameliorate, and β-cell secretion does not deteriorate over time as glucose homeostasis maintains.