Cystic fibrosis (CF) is a genetic condition that causes thick mucus to build up in organs, which can block or damage their function. CF most commonly affects the lungs but can also cause cysts and scarring to occur in the pancreas, liver, sinuses, intestines, and reproductive organs. Complications of CF can include infections, malnutrition, diabetes, bone weakness, and reproductive health issues. Men with CF can struggle with fertility due to the absence of vas deferens, also known as congenital bilateral absence of the vas deferens (CBAVD). The vas deferens are tube-like organs that carry sperm from the testes to the ejaculatory duct. CF may also affect testicular production of testosterone, or hypogonadism, which can be found in up to 45% of men with CF.