Anogenital distance as a biomarker for endometriosis in adolescents: a prospective, matched case-control study

To determine whether anogenital distance (AGD), a potential non-invasive biomarker reflecting prenatal androgen exposure, differs between adolescents with laparoscopically confirmed endometriosis and matched controls.

This IRB-approved, matched case-control study was conducted at a single pediatric hospital between March 2024 and June 2025. Twenty adolescents aged 13-25 years were enrolled: 10 with laparoscopically confirmed endometriosis and 10 controls (three asymptomatic, seven laparoscopically confirmed without endometriosis), matched by age (±1 year) and body mass index (BMI) (±2 kg/m²). AGD was measured under anesthesia from the clitoral surface to the anus (AGD-AC) and from the posterior fourchette to the anus (AGD-AF). Within-pair mean differences were calculated using paired t-tests.

The mean AGD-AC was 9.4 ± 1.2 cm in cases versus 9.7 ± 1.4 cm in matched controls; the mean AGD-AF was 3.5 ± 0.5 cm in cases versus 3.2 ± 0.8 cm in matched controls. Paired t-tests showed no significant differences in either [mean difference AGD-AC = 0.297, 95% CI (-0.85 to 1.44) p = 0.57; AGD-AF = -0.327, 95% CI ( -0.88 to 0.23) p = 0.22]. Substantial overlap was observed across groups, and no significant differences were identified for either AGD measure.

We did not detect a difference in AGD measurements between adolescents with laparoscopically confirmed endometriosis and age and BMI-matched controls; however, with only 10 matched pairs, this study was powered to detect only a large effect, and therefore, these null findings should be interpreted cautiously. Larger longitudinal studies are warranted to assess whether AGD correlates with disease onset, severity, or progression.