PCOS runs in families
PCOS runs in families and often there is a family history of Type 2 diabetes too. Modern genetic analyses have incriminated several genes which predispose to PCOS, but none of these alone is sufficient to cause the disease. Many of the genes identified are involved in the action of insulin and in the production or metabolism of the sex hormones. Male members of the family show symptoms of insulin resistance and have, as a marker, high blood androstenedione, a weak androgen. Environmental factors and lack of physical exercise are also important. We know that weight gain can trigger insulin resistance and PCOS as can steroid medication.
Stress appears to be an important factor contributing to insulin resistance and thus to PCOS. Stress causes cells to develop biochemical abnormalities that initiate and propagate insulin resistance, as well as increasing the stress hormone that antagonizes the action of insulin. Surprisingly, stress causes premature biologic aging; we know that we become more insulin resistant as we age.
Low birth weight babies are more likely to be insulin resistant. Baby girls with low birth weight who then put on weight quickly within the first year or two of life, are especially likely to develop insulin resistance before puberty and to develop PCOS at the time of their first period.