Genetic and environmental factors combine with potential other contributors, including ovarian dysfunction, hyperandrogenism and hypothalamic pituitary abnormalities, to contribute to the aetiology of PCOS.

Twin studies have suggested a large influence of genetic factors in PCOS¹⁶. Although no single genetic abnormality has been identified in PCOS, PCOS is more prevalent among family members with 24-40% of first-degree female relatives of women with PCOS affected¹⁷.  A family history of type 2 diabetes is common.

Environmental factors including sedentary lifestyle result in weight gain. Weight gain exacerbates insulin resistance and accentuates the clinical features of PCOS¹⁸ and weight loss improves these features. In addition, exercise, independent of weight loss may improve insulin resistance, visceral fat and lipids in PCOS¹⁹.

Most women with PCOS, both lean and overweight, have insulin resistance²⁰. In overweight women, this insulin resistance is in excess of that related to BMI²¹. Insulin resistance plays a key aetiological role, contributing to reproductive (hyperandrogenism, anovulation and infertility) and metabolic features (type 2 diabetes, metabolic syndrome and cardiovascular risk factors).

As noted, insulin resistance leads to hyperinsulinaemia which drives ovarian androgen production and increases free androgen levels by reducing sex-hormone-binding globulin (SHBG) level. The combination of increased levels of androgens and insulin underpin the features of PCOS (figure 1). Interestingly, there is a paradoxical expression of IR in PCOS whereby insulin-stimulated androgen production persists, while its role in glucose metabolism is impaired²². Insulin resistance is both genetic and lifestyle related, yet specific causes of insulin resistance and optimal therapies to address it remain unclear.

Figure 1: Basic schema of aetiology and clinical features including reproductive, metabolic and psychosocial features of PCOS.

(Teede et al.²² Reproduced with permission.)

This article first appeared in Australian Doctor - How to treat on 29 August 2008 and has been reproduced here with permission.

 Australian Doctor - How to treat: Polycystic ovary syndrome 437.44 Kb

Content updated 7 September 2011