Heritability of endometriosis

Objective To estimate the relative contribution of genetic influences and prevalence on endometriosis. Design Analysis of self-reported data from a nationwide population-based twin registry. Setting Not applicable. Patient(s) A total of 28,370 women, female monozygotic (MZ) or dizygotic (DZ) twins, who participated in either of two surveys (1998–2002 or 2005–2006). Intervention(s) None. Main Outcome Measure(s) Self-reported endometriosis, validated by medical records. Result(s) A history of endometriosis was reported by 1,228 female twins. The probandwise concordance was 0.21 for MZ and 0.10 for DZ twins. Higher within-pair (tetrachoric) correlation was observed among MZ (0.47) compared with DZ (0.20) twins. The best-fitting model revealed a contribution of 47% by additive genetic factors and the remaining 53% attributed to unique environmental effects. Conclusion(s) Our findings suggest both genetic and unique (nonshared) environmental influences on the complex etiology of endometriosis and support the hypothesis that genes have a strong influence on phenotypic manifestations of endometriosis.