TGFB1 and endometriosis: For example, in a study of Sokolov et al. the concentration of TGF-β in PF did not differ significantly between the women with genital endometriosis and healthy controls34, but two other studies, showed that levels of TGF-β in serum and PF were higher in patients than in controls, and this level, especially in PF, increased with increasing severity of the disease35,40.