Do you insist on rising at five to run each morning, even when your back is
aching, black ice coats the streets, and your wife beseeches you to stay in
bed? Do you only feel good when you’re training for triathlons? Is eating
merely a way to replenish for the next race? Then you, my Spandex-clad friend,
may have an exercise addiction.
But if you want to have children, there's one downside to TRT you should know about. It gives you back your sex life, but it might also reduce your ability to father children as long as you're on it.
"Testosterone replacement therapy has a profound impact on a man's reproductive potential," says urologist Michael Eisenberg, MD. He's director of male reproductive medicine and surgery at Stanford Hospital and Clinics in Palo Alto, Calif.
"In fact," Eisenberg says, "it's been studied as a method of birth control, because 90% of men can drop their sperm counts to zero while on testosterone. By increasing testosterone, you're not going to increase fertility."
Testosterone and Fertility
Testosterone plays an important role in making sperm.
Eisenberg describes the relationship between testosterone and sperm production as part of a "feedback loop." Here's how the system works.
Your brain makes special hormones, called gonadotropin-releasing hormones (GnRH). These hormones signal the testes to make more testosterone, vital for a healthy sperm count.
When you're getting testosterone replacement therapy, testosterone is added into the bloodstream by patches, gels, or other treatment methods.
Your brain interprets this rise in testosterone levels as a sign that you now have enough testosterone. So it stops sending signals to the testes to make more testosterone. But when your testes don't make more testosterone, your sperm production goes down.
A low sperm count makes it harder to conceive a child.
"If you have any kind of reproductive goal, you should not be using TRT," says Eisenberg.
Endocrinologist Spyros Mezitis, MD, PhD, agrees. "You want to increase the patient's own testosterone production in order to get an appropriate sperm sample for pregnancy," says Mezitis, who practices at Lenox Hill Hospital in New York City. "When testosterone comes from the outside, it suppresses the body's production of sperm."
Boosting Fertility When Testosterone Levels Are Low
If you have low testosterone, one way to improve sperm count is with gonadotropin injections. This stimulates the production of sperm. It may be considered as a way to increase a man's fertility when he and his partner are having trouble conceiving a child.
Mezitis says it's standard practice to check a man's sperm count when a couple has difficulty getting pregnant. If his sperm count is low, the next step is to measure his testosterone.
"If it's below normal, we can then inject the signal to produce more testosterone," Mezitis says of gonadotropin injections. "This is done solely to promote fertility."
At this point, Mezitis advises men to seek out a specialist.
"If you have low testosterone and desire fertility, you should work with a reproductive endocrinologist," he says.
You should also make sure to follow a lifestyle of regular exercise and a healthy diet if you want to father a child. Overweight and obese men tend to have lower testosterone levels because excess belly fat converts testosterone to estrogen, another hormone. Shedding those extra pounds will likely have a positive effect on your fertility.
"Losing weight can definitely increase testosterone," says Eisenberg. "It's a very good strategy. It's difficult to lose weight, but for men who are very motivated, it's a good place to start."