Impaired glucose tolerance in Thai adults: serum insulin profiles after a 75 gram oral glucose load.

Serum immunoreactive insulin (IRI) profiles after ingestion of a 75 g oral glucose load were measured in 150 Thai adults (50 men and 100 women, aged 15-71 years) with impaired glucose tolerance (IGT), and 133 control subjects (49 men and 84 women, aged 19-72 years). There were no significant differences in fasting and 30-minute serum IRI levels between subjects with IGT and corresponding age-, sex-, and body mass index (BMI)-matched controls, while subjects with IGT had consistently higher 120-minute serum IRI levels. Early serum insulin responses, as measured by ratio of increment in serum IRI level to that of plasma glucose level 30 minutes after glucose load (delta IRI 30/delta PG 30), were generally low or normal. However, when subjects with IGT are considered individually, there was marked heterogeneity in serum insulin responses, as judged by 120-minute serum IRI, delta IRI 30/delta PG 30, and ratio of sum of serum IRI levels during oral glucose tolerance test (0, 1/2, and 2 hour) to that of plasma glucose levels (sigma IRI/sigma PG). Most of the cases, i.e. 52, 76.7 and 69.3 per cent using previous criteria respectively, had normal insulin responses. We conclude that, 1) Thai adults with IGT generally have higher 120-minute serum IRI levels compared with corresponding age-, sex-, and BMI-matched controls, 2) early serum insulin responses as measured by delta IRI 30/delta PG 30 are generally low or normal, and 3) there is marked heterogeneity in serum insulin responses among these subjects.