There were no significant differences in the mean serum concentrations of GDF9 (Fig. 1A) between controls (11.9 pg/ml, 95% CI: 3.7, 38.5) and patients with endometriosis (12.4 pg/ml, 95% CI: 4.5, 34.2), or in serum BMP15 (Fig. 1B) between controls (24.2 pg/ml, 95% CI: 12.7, 46.1) and patients with endometriosis (21.6 pg/ml, 95% CI: 12.6, 37.2). Here, GDF9 is linked to endometriosis.