A number of factors may compromise male fertility. These include (but are not limited to):
- Obstruction or absence of the tubes of the male reproductive system (the epididymis and vas deferens). This may account for as many as a third of all cases of male infertility.
- Genetic and chromosomal issues.
- Testicular failure (an inability to produce sperm or male hormones).
- Undescended testes (cryptorchism).
- Adverse effects of radiotherapy, chemotherapy, medications or surgery.
- Erectile dysfunction, which may be a consequence of a number of physical or emotional issues, including multiple sclerosis, atherosclerosis (plaque in the arteries), diabetes, stress, anxiety and depression. Being overweight, smoking, eating a fatty diet, or not getting enough exercise may all contribute to this issue, as may the use of recreational drugs or excessive consumption of alcohol.
- Stress, which may cause sperm count to decline.
- Environmental or occupational exposure to pesticides, heavy metals, or heat may also be involved .
In around 10% of couples that have difficulty conceiving, no cause can be determined in either the male or female partner.