What can cause infertility in men?

Male infertility has a wide variety of causes, which can be broken down into several major groups:

• Hormonal problems, such as low levels of testosterone or thyroid hormone.

• Problems with the testicles, including abnormal growth or development, or damage from trauma and infections.

• Problems with the flow of sperm within the male reproductive organs, including blocked tubes that transport sperm, genital infections, varicose veins (varicoceles) within the scrotum, or problems with ejaculation.

• Abnormal sperm function.

• Inherited or chromosomal disorders, including cystic fibrosis and Klinefelter's syndrome.

• Exposure to toxins, such as radiation or industrial chemicals.

• Medications and drugs, including psychiatric medications, alcohol, and anabolic steroids used for bodybuilding.

• General illnesses, including kidney disease, cirrhosis and malnutrition.

In up to 50% of infertile men, no specific cause can be identified.