PCOS Twin Study - Environmental Factors in the Development of Polycystic Ovary Syndrome, Phase 2

Polycystic Ovary Syndrome, or PCOS, is the most common endocrine disorder in women. Depending on the strictness of the diagnostic criteria used, it is thought to occur in about 6-10% of all women, many of whom do not know they have the syndrome. Women with PCOS produce abnormally high levels of male hormones (hyperandrogenism); this counteracts their ovaries' ability to make enough of the female hormones estrogen and progesterone needed for normal menstruation. PCOS is the number one cause of hormonally related infertility and also increases women's risks for diabetes, high blood pressure, hypercholesteremia, cardiovascular disease and certain cancers. It is currently unclear to what extent PCOS and PCOS-associated traits (hyperandrogenism, hyperinsulinemia, insulin resistance, type 2 diabetes, dyslipidemia, hypertension, obesity, and coronary artery disease) are the results of environmental factors or genetic predisposition. Therefore, the NIEHS Program in Clinical Research is conducting a multi-phase twin study to measure the extent of PCOS heritability and to identify environmental and genetic factors involved in the development of PCOS. The proposal described here is for Phase 2 of this study. The goals of Phase 2 are to: 1) establish more reliable concordance rates and baseline heritability estimates for PCOS in MZ and DZ twins; and 2) establish a cohort of intact MZ and DZ female twin pairs with PCOS as a resource for future studies.

In Phase 1, about 1500 individual female twins were identified from the Mid-Atlantic Twin Registry (MATR) based on self report of a history of irregular periods and/or cystic ovaries in the MATR General Health Screening Questionnaire. Those twins were surveyed by phone for other traits associated with PCOS. In Phase 2, the twins most likely to have PCOS based on their answers to the Phase 1 phone survey will be recontacted for further PCOS screening. One or both twins in a pair will be screened for elevated levels of testosterone (total and free testosterone, bioavailable testosterone or BaT; free androgen index or FAI). Hyperandrogenism is one of the hallmark traits of PCOS and can be exhibited either biochemically (elevated testosterone) or clinically (hirsutism, acne, hair loss, alopecia, other). If one twin in a pair has an elevated BaT level, then both twins in the pair will be asked to undergo a medical evaluation for PCOS confirmation. This includes a physical exam, medical history, ultrasound, 2-hour glucose tolerance and other biochemical blood tests, and a Ferriman-Gallwey evaluation for abnormal hirsutism (another characteristic of PCOS). The women will also be tested for pregnancy and zygosity. Their female co-twins will be invited to undergo a similar medical evaluation.

Depending on their PCOS traits, twin pairs in which neither member has elevated testosterone levels might be asked to undergo the medical evaluation as well. In clinical practice, PCOS diagnoses are often made on women with normal testosterone levels if they have other certain PCOS traits. The determination to include pairs in which both members have normal testosterone levels will be made depending on their collective PCOS traits that they reported on their Phase 1 survey.