Insulin sensitivity in women: a comparison among values derived from intravenous glucose tolerance tests with different sampling frequency, oral glucose tolerance test or fasting

Objective: To determine the correlation between insulin sensitivity (S-I) obtained by the minimal model method applied to a frequently sampled (n = 33) intravenous glucose tolerance test (FSIGT(33)), and values obtained by reduced FSIGTs, oral glucose tolerance test (OGTT), or fasting. Design: Retrospective analysis on tests performed in prospective studies. Methods: A total of 78 FSIGT(33), and 59 OGTT were performed in non-diabetic women of which 10 were young cyclic females in the early follicular menstrual phase, 10 were young non-obese subjects with polycystic ovary syndrome (PCOS) and 30 were in post-menopause. Some of these individuals were investigated both prior to and during specified treatments. FSIGT(33) was transformed into FSIGT(22) and FSIGT(12) by removing samples from the analysis. Values of S-I derived from reduced FSIGTs or calculations performed on glucose and insulin values observed in fasting conditions and/or during OGTT were related to those of FSIGT(33.) Results: S-I, values derived from FSIGT(33) were highly correlated with those derived from FSIGT(22) (r = 0.965) or FSIGT(12) (r = 0.955), but were only weakly correlated with those derived from fasting or OGTT calculations (r below 0.5). Between-group (PCOS vs normal) or within-group (prior to and during treatment) comparisons showed that reduced FSIGTs were only slightly less powerful than FSIGT(33) in detecting differences in S-I. Conclusions: In noti-diabetic women, reduced FSIGTs but not calculations based on fasting or OGTT values may be used in place of FSIGT(33) to document S-I and its variation.