Even though the hormonal imbalance that produces the symptoms of polycystic ovarian syndrome (PCOS) is becoming better understood, the disorder’s actual cause is unknown.

Research suggests a link between PCOS and excess insulin in the blood. Many women with PCOS have a family history of diabetes. Insulin is a hormone produced in the pancreas that enables body cells to use glucose (blood sugar) for energy. Women with PCOS have a decreased sensitivity to insulin, also known as insulin resistance. Through several mechanisms, excess insulin is believed to boost the production of androgens (male hormones) in the ovaries. This, in turn, brings about many of the symptoms associated with PCOS, such as excessive weight gain and excessive hair growth throughout the body.

Research has indicated that PCOS may be hereditary. Many women afflicted with PCOS have a family history of complications commonly associated with the disorder. Their relatives need not have been diagnosed with PCOS, but they may have experienced related problems. These conditions could include irregular periods, absence of menstruation (amenorrhea), an inability to become pregnant, excess androgen production, insulin resistance, diabetes, obesity and/or hirsutism.

PCOS is less common among women as they get older and is extremely uncommon after menopause, although cases have been reported.