CFTR and cystic fibrosis: Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) are the pathogenic basis of cystic fibrosis (CF) [61] and can lead to obstructive azoospermia (OA) due to 60–70% congenital bilateral absence of the vas deferens (CBAVD), which accounts for 1–2% male infertility and is the only known genetic cause of CBAVD [62], and is the only genetic factor at play in CBAVD [63].