TGFB1 and congenital bilateral aplasia of vas deferens from CFTR mutation: CAVD has a pathological mechanism similar to atherosclerosis, and Liu et al. indicated an inhibitory effect of metformin on the osteoblastic differentiation of AVICs induced by TGF-β1 by inhibiting β-catenin pathway; however, only few studies have reported the effectiveness of metformin on CAVD (Liu et al. 2018).