Why are most males with Cystic Fibrosis sterile?

Cystic Fibrosis (CF) is a genetic disorder caused by mutations in the CFTR gene, leading to abnormal chloride transport across epithelial cells. Most males with CF are sterile primarily due to the incomplete development of the vas deferens, a structure critical for the transport of sperm from the testes to the urethra. In many affected males, the vas deferens is either absent or obstructed, a condition known as congenital absence of the vas deferens (CAVD). This anatomical defect prevents the passage of sperm, resulting in infertility.

Although other factors may contribute to aspects of reproductive health in males with CF, such as potential complications arising from lung function or hormonal deficiencies, the primary reason for sterility in these individuals is the developmental issue with the vas deferens itself. Genetic mutations in sperm, while they might affect fertility in some contexts, are not relevant here because the absence of a functioning vas deferens halts the process before sperm can even contribute to conception. Thus, the profound impact that CF has on the reproductive anatomy of males is the key factor explaining their sterility.