Cuhna Filho et al. analyzed the levels of insulin-like growth factor-1 (IGF-1) and IGF-binding protein-1 and -3 (IGFBP-1 and IGFBP-3) in the follicular fluid environment of infertile patients with endometriosis and concluded that the expression of both proteins was not significantly different among the groups [45]. Here, IGFBP1 is linked to endometriosis.