The precise cause is unknown for years. However , experts in women health ascribed PCOS to genetic factors because the disease was found to run in families
one of the causes is defective insulin receptor. this insulin resistance causes hyperinsulinemia which affects the hepatic and ovarian function causing hyperandrogenemia, weight gain, acne and anovulation
The exact cause of polycystic ovary syndrome (PCOS) is unknown. However, it is assumed that genetics and hormonal imbalances play role in development of this disorder.
Accumulating evidence suggests that PCOS might be a complex multigenic disorder with strong epigenetic and environmental influences, including diet and other lifestyle issues because of its frequent association with abdominal adiposity, insulin resistance, obesity, metabolic disorders and cardiovascular risk factors. The link below is a recent paper that will enlighten you on PCOS.