To examine the role of genetic and environmental factors in polycystic ovary syndrome (PCOS) by using the classic twin model.
Outpatient clinic of the Royal Hospital for Women, Paddington, Sydney, New South Wales, Australia.
A group of 19 monozygotic (MZ) and 15 dizygotic (DZ) twin pairs identified from the national twin register.
Ultrasound, clinical, and biochemical parameters were used to define PCOS.
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.
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.