Factors Responsible for Development From Normal Glucose Tolerance to Isolated Postchallenge Hyperglycemia

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Abstract
OBJECTIVE—Isolated postchallenge hyperglycemia (IPH), defined as fasting plasma glucose (FPG) level 1) normal glucose tolerance (NGT), defined as FPG level n = 89); 2) impaired glucose tolerance (IGT), defined as FPG level n = 94); and 3) IPH (n = 48). We compared the three groups for insulin secretion (insulinogenic index) and insulin sensitivity (index of insulin resistance using homeostasis model assessment [HOMA-IR]). RESULTS—The insulinogenic index in IPH was the lowest of the three groups (P < 0.001 versus NGT). The HOMA-IR in the IGT and IPH groups were significantly higher than in the NGT group (P < 0.001), but both were similar. By linear regression analysis, the insulinogenic index rather than fasting insulin or HOMA-IR was the more significant factor in the 2-h PG level in IGT and IPH. CONCLUSIONS—Subjects with IPH exhibited distinctly impaired early-phase insulin secretion and only mild insulin resistance, indicating that reduced insulin secretion is the primary determinant of deterioration from NGT to IGT and IPH in development of type 2 diabetes in these subjects.
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