Marked Hyperinsulinaemia in Postmenopausal, Healthy Indian (Asian) Women

Abstract

The effect of the menopause on insulin metabolism has not received specific attention in populations prone to non-insulin-dependent (Type 2) diabetes mellitus (NIDDM). Insignificant or slight alterations in insulin levels have been reported in postmenopausal women of mainly European ancestry. We thus report on the results of a cross-sectional study on the correlates of fasting insulin levels in 177 healthy, Indian nurses aged between 25 and 55 years. Fasting insulin concentration was markedly higher in the 75 postmenopausal subjects (23.9 mU I-1) than in the 102 premenopausal women (11.7 mU I-1 (p < 0.0001). Forty-three (57%) of the postmenopausal subjects had insulin values more than 20 mU I-1 (the upper normal limit). Stepwise regression analysis on the entire group revealed menopause (p < 0.0001), waist:hip ratio (p = 0.0001), apolipoprotein E genotype (p = 0.002), and the testosterone: sex hormone binding globulin ratio (p = 0.0002) as statistically significant, independent predictors of log insulin levels. Age did not account for the difference between premenopausal and postmenopausal subjects. The apolipoprotein E genotype emerged as a significant correlate of insulin levels, only in postmenopausal women: epsilon 3/3, 26.3 mU I-1; epsilon 3/4, 51.8 mU I-1 (p = 0.0007). Hyperinsulinaemic postmenopausal subjects had higher fasting glucose levels than normoinsulinemic nurses (p = 0.03), but glycosylated haemoglobin and fructosamine values were all within the normal range. Thus fasting hyperinsulinaemia was marked and common among a group of healthy, postmenopausal Indian nurses below the age of 55 years, suggesting that the menopausal transition may permit or provoke insulin resistance in this susceptible population.