The role of leptin in the establishment and propagation of endometriotic lesions has also been shown in experimental models [59], but case-control analysis within the large cohort of NHS II failed to show statistically significant associations between endometriosis and leptin, even after adjustment for BMI (RR 1.2, 955 CI 0.7–2.0, p 0.72) [60]. This evidence concerns the gene LEP and endometriosis.