β‐Cell function in postmenopausal women with isolated post‐challenge hyperglycemia

BACKGROUND: Isolated post-challenge hyperglycemia (IPH) is an early stage of type 2 diabetes mellitus (T2DM), with fasting glucose <126 mg/dL and 2-h glucose ≥200 mg/dL. Observations of insulin secretion profile in subjects with IPH may provide an insight into the pathogenesis of T2DM in older women. METHODS: We recruited 555 naturally postmenopausal women without a history of T2DM to the present study. All participants received a 75-g oral glucose tolerance test to determine whether they had IPH. General linear models were used to compare differences in glucose metabolism among subjects. RESULTS: Early phase insulin responses to oral glucose were significantly decreased in women with IPH versus those with impaired glucose tolerance (IGT) and normal glucose tolerance (geometric mean 95% confidence interval insulinogenic index 61 54-79 vs 90 83-97 and 105 96-116, respectively; P < 0.0001). In addition, there were significant decreases in late-phase insulin release as metabolic status shifted from normal glucose tolerance to IGT to IPH. In the present cohort, the relative contribution of early insulin secretion to 2-h glucose was no longer significant ( P = 0.15) after multiple factors, including indicators of insulin resistance and late-phase insulin release, were entered into the regression model simultaneously. CONCLUSIONS: The results demonstrate that postmenopausal women with IPH are characterized by impaired β-cell function. There were significant decreases in early and late-phase insulin release as glucose intolerance escalated. Disturbance in β-cell function seems to be an important factor associated with early T2DM in postmenopausal women.