Genetics and Family History.

A number of studies point to a strong familial predisposition for PCOS and insulin resistance, the primary mechanism of the condition. There is less intra-familial variation in insulin resistance than inter-familial variation supporting the closeness in families for these traits. Also, there are ethnic differences in insulin resistance. For instance, the highest rates of insulin resistance are found in Pima Native Americans (50%), while 25 % of Native Australians and Peninsular Arabs have insulin resistance compared to 4 % of Northern Europeans.

The difficulty in studying the genetics of PCOS is due to the variable expression of the condition, poor agreement of diagnostic criteria, and lack of a male PCOS patient. Additionally, factors such as environment (fat/carbohydrate intake), exercise, peri-pubertal stress are important but difficult to reliably quantify.

In a study using strict diagnostic criteria, investigators from Birmingham, Alabama studied 218 patients. 168 (77%) had another female relative with PCOS, 1f the mothers and sisters, 1aternal and paternal aunts had PCOS. This was consistent with an autosomal dominant with variable phenotype inheritance. In the next few years, it is hoped that the actual gene defects will be discovered. Studies have shown with age and weight matched controls that women with PCOS and without PCOS had similar nutrient intake (calories, carbohydrates, protein) and physical activity (light, moderate, vigorous). Lean women with PCOS did, however, have a lower caloric intake. Thus, the obesity in PCOS is not simply because the patients are eating more and exercising less. Clearly, individual metabolism plays a role.