Wertel et al. [15] compared the level of serum and peritoneal level of leptin in different stages of endometriosis in two study groups, fertile and nonfertile, and the study revealed that higher level PF leptin concentration was observed in patients with stages III and IV of endometriosis than in those with the minimal stage of the disease, a similar result from our study in serum leptin level. This evidence concerns the gene LEP and endometriosis.