In patients with moderate-severe endometriosis (Stage III–IV), serum Gal-1 levels were 18.5 ± 3.99 ng/mL (95% CI: 17.5–19.4) at T1, decreasing to 16.4 ± 3.62 ng/mL (95% CI: 15.5–17.3) at T2. This evidence concerns the gene LGALS1 and endometriosis.