Male infertility has a variety of causes

Q: My wife and I have tried to get pregnant for over a year. We're going to be tested soon to see if anything is wrong. I'm worried that the problem lies with me. What are some reasons for a man to be infertile?

A: About one in seven couples in the United States are unable to conceive a child after trying for one year. The infertility is caused either by the man alone (about 40 percent of the time), by the woman alone (about 40 percent of the time) or by both partners (about 20 percent of the time). So it is possible that something about you is responsible for your wife's difficulty with becoming pregnant.

Male infertility may be caused by a variety of problems:

• Hormonal problems: For example, low levels of testosterone (the main male hormone) or thyroid hormone.

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

• Problems with the flow of sperm: This may include blocked tubes that transport sperm, or problems with ejaculation.

• Abnormal sperm function: This may affect the ability of sperm to fertilize an egg.

• Exposure to toxins: Radiation, for example, or industrial chemicals.

• Medications and drugs: These include psychiatric medications, alcohol, and anabolic steroids used for bodybuilding.

Your evaluation will likely begin with a semen analysis. This test measures the amount and quality of your semen and the number and quality of sperm. If your semen analysis is normal, you may not need further testing.

If your semen analysis is abnormal, your doctor will take a complete medical history and test your hormone levels. The doctor will also perform a physical exam. He or she will look for evidence of genital infections, blocked sperm tubules in the testes or shrinkage of the testicles.

Particularly if the physical examination indicates there is a problem, various tests often are ordered. You may need an ultrasound of the testicles and scrotum to picture any possible blockages. Your sperm may be tested. The role of the sperm is to swim toward a woman's egg and to fertilize it. The ability of the sperm to swim in semen can be studied with a microscope. So can the ability of your sperm to penetrate a hamster egg. If it can't, it will likely not be able to penetrate a human egg.

Genetic tests may be performed. Several gene defects have been identified in recent years. Finally, a biopsy of the testicles may show any of several diseases that impair the production of sperm.

If there is a specific reason for your infertility, it may be possible to treat. If you have no treatment options, consider assisted-reproduction techniques, such as artificial insemination or in vitro fertilization. Problems with fertility often have a solution - with a healthy baby as a result.

• Dr. Komaroff is a physician and professor at Harvard Medical School. For questions, go to AskDoctorK.com.