Objective: To evaluate the characteristics of daily glucose change, insulin sensitivity, and insulin release in polycystic ovary syndrome (PCOS) women with normal glucose tolerance.
Methods: Oral glucose tolerance test (OGTT) with 75 g glucose was conducted on 20 PCOS women with normal glucose tolerance and 20 age-matched healthy women with normal menstruation. Before the glucose uptake and 30, 60, and 120 min after samples of venous blood were collected to detect the blood glucose and insulin. Continuous glucose monitoring system (CGMS) was used to monitor the glucose concentration of subcutaneous interstitial fluid so as to reflect the blood glucose level. Mean blood glucose level (MBG) and its standard deviation (SDBG), mean amplitude of glycemic excursion (MAGE), peak level of postprandial plasma glucose as well as its peaking time during a 48-hour period CGMS were calculated. Stumvoll first-phase and second-phase (1st PH and 2nd PH) insulin release during OGTT were evaluated by Stumvoll formula, whereas baseline insulin release by HOMA-B. Insulin sensitivity index (ISI) was evaluated by Cederholm formula.
Results: (1) The 1-hour and 3-hour plasma glucose levels during OGTT of the PCOS group were higher than those of the control group (P < 0.01 and P < 0.05 respectively). The fasting insulin level and insulin levels 30, 60, 120, and 180 min after the glucose uptake during OGTT of the PCOS group were all significantly higher than those of the control group (all P < 0.01). (2) The daily MBG, SDBG, and MAGE of the PCOS group were (5.43 +/- 0.44), (0.66 +/- 0.24), and (1.46 +/- 0.47) mmol/L respectively, all similar to those of the control group [(5.3 +/- 0.5), (0.67 +/- 0.27), and (1.7 +/- 0.7) mmol/L respectively, all P > 0.05]. The peaking time of post-breakfast plasma glucose level of the PCOS group was (40 +/- 18) min, significantly longer than that of the control group [(30 +/- 10) min, P < 0.05]. (3) The ISI of the PCOS group was 64 (59 - 81), significantly lower than that of the control group [95 (78 - 102), P < 0.01]. The Stumvoll 1st PH and 2nd PH insulin release levels of the PCOS group were 1779 (1411 - 2194) mU/L and 440 (361 - 545) mU/L respectively, both significantly higher than those of the control group [1217 (1056 - 1477) and 320 (283 - 375) mU/L respectively, P < 0.01 and P < 0.05].
Conclusion: With normal glucose tolerance, the PCOS women show (1) a backwardly-shifted peak of glucose -stimulated insulin secretion, (2) an abnormal mode of daily glucose change characterized by a delayed peak of post-breakfast plasma glucose level, and (3) significant decrease of peripheral insulin sensitivity with compensated increase of insulin secretion.