A twin study of polycystic ovary syndrome

OBJECTIVE: To examine the role of genetic and environmental factors in polycystic ovary syndrome (PCOS) by using the classic twin model. SETTING: Outpatient clinic of the Royal Hospital for Women, Paddington, Sydney, New South Wales, Australia. PATIENTS: A group of 19 monozygotic (MZ) and 15 dizygotic (DZ) twin pairs identified from the national twin register. INTERVENTIONS: Ultrasound, clinical, and biochemical parameters were used to define PCOS. RESULTS: Eleven pairs of twins (5 MZ, 6 DZ pairs) were scan-discordant (i.e., one twin had scan-PCOS and the co-twin did not). Model-fitting analysis suggested that fasting insulin level, androstanediol glucuronide, and body mass index (BMI) were significantly influenced by genetic factors. CONCLUSION: This study suggests that PCOS is not the result of a single autosomal genetic defect, but rather environmental factors, perhaps both intrauterine and extrauterine, are involved in the pathogenesis of this disorder or that PCOS may be an X-linked disorder or the result of polygenic factors. However, fasting insulin level, androstanediol glucuronide, and BMI did appear to be under significant genetic influence.