You’ve been bombarded with health advice since you were a kid, and by now you’re probably pretty adept at spotting the good and ditching bogus info. You no longer believe you’ll go blind from masturbating, aren’t afraid to swim after shoveling in a snack, and know that drinking 8 glasses of water per day is more of a suggestion than gospel. But other health misconceptions still abound, particularly when it comes to testosterone.
“The internet can be great for getting information, but it matters where you get your sources,” says urologist Joshua Calvert, M.D. “I have guys who come into my office weekly who ask which testicle produces testosterone, does tanning your balls increase testosterone. My patients see so much conflicting—and often just plain inaccurate—information about testosterone on the internet.”
So let’s bust some common testosterone myths and drop some science-backed knowledge.
The Science Behind Testosterone
“Testosterone is the predominant male sex hormone produced in the testicles, and to a lesser degree in the adrenal glands,” says Calvert. When testosterone levels peak in your late teens and early 20s, the hormone is responsible for body hair and penis growth. But throughout your life, T is also critical to your general well-being.
T works with other hormones and androgen receptors (ARs) in other tissues to regulate loads of processes. “Testosterone is needed for sperm production, muscle growth and strength, libido, and red blood cell production,” says Calvert.
What Does Testosterone Do (and What Doesn’t it Do)?
It’s beyond those basic T facts where things get murky, and testosterone myths creep in. Let’s tackle them one by one.
Can Testosterone Increase Muscle Size?
Absolutely. According to Calvert, muscle cells have a very high concentration of AR’s. If your T levels are between 264 and 916 ng/dL, according to a study in The Journal of Clinical Endocrinology & Metabolism (1) those ARs are activated and your body can put on muscle. Note that 265 ng/dL is still considered low by American Urological Society guidelines.
If you have low T (anything below 300 ng/dL), you may struggle to build muscle, no matter how much time you put in at the squat rack.
Getting your levels back to normal through TRT or diet changes typically solves the problem. “Increased muscle mass and decreased fat is very common in men who go from low to normal testosterone levels,” says Calvert.
Does Testosterone Cause Hair Loss?
It can–but it’s complicated. Testosterone plays more of a role with the lush jungle in your armpits than the hair on your head.
“Testosterone is required to maintain hair growth cycles, particularly for body hair, but to a lesser extent hair on your head,” explains Calvert. “So guys with low testosterone tend to have less body hair compared to their buddies who have normal T levels.”
Male pattern baldness is actually related to dihydrotestosterone (DHT), a byproduct of testosterone. DHT is made from testosterone by an enzyme called 5α-reductase. If your 5α-reductase levels are too high, it can lead to higher DHT levels and a less-full head of hair.
DHT is five times more potent than free testosterone (the type your body uses), says Calvert. Finasteride, a prescription medication for hair loss, works by blocking the conversion of testosterone to DHT.
Testosterone replacement therapy (TRT) can also cause DHT levels to increase. “You can imagine with uninhibited increased T levels, your body combats that by increasing the level of DHT,” says Calvert. “This is why I don’t recommend my patients to get too high on their TRT. I prefer guys to be in a range of about 750 – 900 ng/dL.”
Does Testosterone Make You Hornier?
One of testosterone’s primary jobs is to regulate your sex drive. Researchers are clear on the exact mechanics, but low libido is one of the most common symptoms of low T, says Calvert. And research has shown that men with lower sex drives are more likely to be testosterone deficient (2).
“Testosterone deficiency is associated with decreased libido–and combating that with testosterone supplementation increases libido,” he says. “Being hornier is without a doubt the number one reported improvement I hear from guys who start TRT.”
Does Testosterone Increase Penis Size?
We hate to disappoint you, but although T is responsible for penis growth during puberty, afterwards it doesn’t have the same benefit.
That said, T can help your member. “Testosterone can give you more dependable erections, which some people perceive as increased penis size–but there is no way to increase penis size–no matter how many internet pop-ups you see. It just doesn’t happen,” says Calvert.
And honestly, you’re probably are packing plenty to get the job done, according to a study in the journal Psychology of Men & Masculinity. A full 86 percent of women in the study said they were satisfied with their partner’s penis size (3).
Do Cold Showers Increase Testosterone?
This is a common internet myth–and that’s exactly what it is.
“It is rooted in the TRUE idea that prolonged exposure to heat decreases testicular production of testosterone and thus sperm,” explains Calvert. “People thus think that if hot water is bad, cold water is good.”
That said, hot water can have a negative effect on sperm count. “For my patients struggling with infertility, I do recommend avoiding hot-tubs and saunas, but I don’t recommend that they swim in icy lakes,” says Calvert.
Does Semen Retention Increase Testosterone?
While the NoFap movement has gained popularity in recent years, it does nothing for your testosterone levels.
“People have been falsely attributing lack of ejaculation to health benefits for thousands of years,” says Calvert. “There are no credible articles to suggest that semen retention boosts testosterone.”
Does Testosterone Impact Fertility?
For couples trying to conceive, testosterone injections might make conceiving more difficult–but not impossible.
“In the 1990’s the WHO studied injectable testosterone as a form of male birth control, and it was found to be about 97% effective,” says Calvert. “So it’s basically like trying to get pregnant while wearing a condom.”
Another option your doctor may prescribe instead of TRT is Clomid (also known as clomiphene), which can also help boost T levels.
Can Testosterone Make You Taller?
Yes. And no. During puberty, your body needs testosterone to grow. But once you stop growing, adding additional T won’t help your dreams of playing in the NBA.
Does Testosterone Make You Angry?
Guys who abuse anabolic steroids to boost their muscle mass and gym performance can get aggressive (and are the reason the term ‘roid rage’ exists). But you don’t have to juice to know that testosterone can impact your mood and emotions.
And having too little testosterone can make you as irritable and cranky as having too much, says Calvert.
Experts don’t completely understand the connection between testosterone levels and mood. It could be that T affects the production of brain cells and neural connections (4) or that it regulates feel-good neurotransmitters (5).
Going on TRT can also make you cranky in the short term. “A temporary moodiness, aggression, and irritation is common in men who start on TRT, but it usually goes away after a few weeks,” says Calvert.
“The best way to combat this is to expect it and let your loved ones know that they can expect some temporary mood changes.”
Does Zinc Increase Testosterone?
Despite what you may have heard, this supplement is not a ‘magic pill’ to help increase your T levels.
“The evidence that does exist is often contradictory, negative or lacks evidence,” says Calvert.
Zinc does help support normal testosterone levels, but the largest, most recent review (6) showed that there is minimal evidence to suggest that “testosterone boosters”—supplements that often contain zinc—can give your T levels a lift.
The Bottom Line
Testosterone is responsible for not only your sex drive, but so many other functions in the human body. If you suspect your T levels are tanking, talk to your doctor or urologist about getting your T levels tested and possible treatments to help get your testosterone levels back to normal.