Objective: To determine the rate of clinically evident polycystic ovary syndrome (PCOS) among first-degree female relatives within families with a proband affected by PCOS.
Design: Clinical and biochemical evaluation of the mothers and sisters of 93 patients with PCOS. The diagnosis of PCOS was established by:  a history of oligomenorrhea,  clinical evidence (i.e., hirsutism) or biochemical evidence (i.e., elevated total or free T) of hyperandrogenism, and  the exclusion of related disorders.
Setting: Tertiary care university.
Patient(s): Patients with PCOS and their mothers and sisters.
Intervention(s): Interview, physical examination, and hormonal testing on blood samples were performed for all subjects.
Main outcome measure(s): The presence of hirsutism and hyperandrogenemia was determined in the mothers and sisters of the patients with PCOS.
Result(s): Of the 78 mothers and 50 sisters evaluated clinically, 19 (24%) and 16 (32%) were affected with PCOS, respectively. A higher rate of PCOS was observed when only premenopausal women not taking hormones (i.e., untreated) were considered (i.e., 35% of mothers and 40% of sisters), consistent with amelioration of symptoms with hormonal therapy or aging. These rates of PCOS are significantly higher than that observed in our general population (approximately 4%) and suggest the involvement of a major genetic component in the disorder.
Conclusion(s): The rates of PCOS in mothers and sisters of patients with PCOS were 24% and 32%, respectively, although the risk was higher when considering untreated premenopausal women only.