Sex hormone-binding globulin and androgen levels in immigrant and British-born premenopausal British Pakistani women: evidence of early life influences?

Abstract

In women raised insulin levels are associated with low sex hormone-binding globulin (SHBG) and high androgen levels, which are in turn linked to infertility. Since insulin resistance and hyperinsulinaemia are major health problems for South Asians living in western countries we predicted that British Pakistani women would have low SHBG and raised androgen levels compared to European women. Given low birth weights in Pakistan, and known links between low birth weight and insulin resistance in later life, we also predicted that immigrant women, born in Pakistan, would have lower levels of SHBG and higher levels of androgens than British-born British Pakistani women. We assessed SHBG, testosterone and free androgen index (FAI) from a single serum sample taken on day 9-11 of the menstrual cycle from 20-40 year old women living in the UK, 30 immigrants from Pakistan, 30 British-born British Pakistani women and 25 British-born women of European origin. Age-adjusted analyses showed that there were no significant differences in SHBG, testosterone or FAI between the British-born Pakistani and European origin women. However, immigrant British Pakistani women had a significantly higher FAI than British-born British Pakistani women. Adjustment for body mass index, waist to hip ratio and smoking status did not affect these results, but further adjustment for height, a marker of early environment, reduced the p value to below significance. It is possible that the poorer early environment of immigrant British Pakistani women was at least partially responsible for their relatively high levels of free androgens.