Insulin response to oral glucose in healthy, lean young women and patients with polycystic ovary syndrome

Abstract

Background and aim. Insulin resistance and consequent hyperinsulinemia are common among patients with polycystic ovary syndrome (PCOS). Ethnicity and dietary habits affect insulin levels. There is little published information from India on insulin levels in PCOS patients. Thus the present study aimed to determine the insulin response to oral glucose in women with PCOS and healthy women.

Methods. In a case–control study design, women with PCOS and lean healthy women without a family history of diabetes mellitus underwent oral glucose tolerance testing. Samples were collected at 0, 1 and 2 h after glucose ingestion.

Results. Two hundred and eighty-five women with PCOS and 27 lean healthy young women were enrolled into the study. The mean age of controls was 22.8 ± 4.5 years (range 15–32 years) and their mean body mass index (BMI) was 19.7 ± 2.6 kg/m². Mean blood glucose at 0, 1 and 2 h was 88.2 ± 7.2, 115.5 ± 25.5 and 91.8 ± 20.5 mg/dl, respectively. Corresponding plasma insulin levels were 5.8 ± 1.1, 32.7 ± 26.5 and 14.6 ± 9.6 mIU/l. Peak insulin levels were seen at 1 h and these came down to less than 40% of the peak value by 2 h. Glucose/insulin ratio at 0, 1 and 2 h was 15.6 ± 3.1, 7.0 ± 3.1 and 11.4 ± 7.0. Homeostasis model assessment of insulin resistance (HOMA-IR) was 1.2 ± 0.2.

The age of the PCOS women ranged from 15 to 40 years (mean 23.4 ± 6.2 years) and their BMI ranged from 16.4 to 50.4 kg/m² (mean 27.7 ± 6.3 kg/m²). One hundred and seventy-six (62%) PCOS patients had normal glucose tolerance (NGT), 39 (14%) had impaired fasting glucose (IFG), 49 (17%) had impaired glucose tolerance (IGT) and 21 (7%) had type 2 diabetes mellitus (T2DM). Insulin response was higher in women with PCOS. Peak insulin was observed at 1 h. The difference between 1-h and 2-h post-glucose insulin decreased with worsening glucose tolerance. Both plasma insulin and BMI showed a rising trend from NGT to IFG to IGT. There was no further increase in either insulin or BMI from IGT to T2DM. Glucose/insulin ratio at 0, 1 and 2 h was lower (8.3 ± 4.2, 2.0 ± 1.6 and 3.2 ± 3.5) than that of healthy controls. HOMA-IR was 3.1 ± 3.0.

Conclusion. Women with PCOS had an exaggerated insulin response to glucose. Thirty-eight percent of PCOS women had some form of abnormal glucose tolerance. Greater insulin response was seen with impairment of glucose tolerance. Obesity had no effect on fasting insulin or insulin response to oral glucose in PCOS women with NGT.

Keywords:

• Insulin
• insulin resistance
• polycystic ovary syndrome