What steroids do to your balls

Gym gear really does shrink testicles. How steroids switch off the balls' own testosterone and sperm, what the studies say about recovery and why it is not guaranteed

Every gym has the joke about the guy whose arms grew while something else shrank. It is one of the rare gym myths with solid physiology behind it. Anabolic steroids really do shrink the balls, the reason is simple once you see how the system works, and the good news and the bad news both come from the same studies.

This is not a page about whether you should use them. It is about what happens below the belt if you do, or if the man you are dating does.

Gym culture, by the numbers

In 2000, researchers handed questionnaires to 772 gay men in six central London gyms. 15.2% had used steroids in the previous 12 months and 11.7% had injected them. HIV-positive men were the most likely to have used them, some for medical reasons. Nearly all users, 96.4%, reported at least one side effect, and the commonest was testicular atrophy, in 51%.

That was one city, one year and a self-selected sample, so it is not a prevalence figure for gay men in general. A more recent Dutch study puts use among amateur strength athletes overall at an estimated 4-6%. Either way, if you spend time in gyms or on apps full of gym selfies, you will meet users.

Why the balls shrink

The testicles have two jobs: making testosterone and making sperm. Both are run from the brain. The hypothalamus signals the pituitary gland, which releases two hormones, LH and FSH. LH tells the Leydig cells in the testicles to make testosterone; FSH, together with a very high concentration of that testosterone inside the testicle, drives sperm production in the long coiled tubules that make up most of each ball (see Balls).

This system runs on feedback. When the brain senses enough testosterone in the blood, it turns LH and FSH down. Inject testosterone or a related steroid, and the brain sees plenty of hormone and cuts the signal almost to zero. A meta-analysis of studies on athletes and recreational users found that LH, FSH and the body's own testosterone all fell significantly during use.

Without LH, the Leydig cells stop producing. Without FSH and local testosterone, the sperm factory slows or stops, even though the blood is full of steroids, because what reaches the testicle from outside is far less than the testicle makes for itself. Idle tubules shrink, and so do the balls. Among 100 Dutch amateur athletes followed through a self-chosen cycle, 77% had a sperm count below 40 million during use. In an older German study of 41 bodybuilders, 24 had sperm counts below the normal limit, against 5 of 41 non-users; their doses were up to 40 times those used in medicine.

Do they come back?

Mostly, slowly, and not for everyone. The reassuring data first:

• In the Dutch cohort, testosterone levels had returned to baseline three months after the end of the cycle in most men, while sperm production took about a year.
• An Australian study of current and past users found that, apart from testicle size, past users were no different from non-users. Recovery took on average 7 to 11 months for the hormones and about 14 months for sperm output, and the longer a man had used, the slower his sperm came back.
• In the German bodybuilders, sperm counts were in the normal range in those who had stopped more than four months earlier.

Now the other side. At the one-year mark in the Dutch study, 11% of men still had testosterone below normal and 34% still had sperm counts under 40 million. In the Australian study, smaller testicles were one of the few things that had not recovered. In a group of former long-term users in Massachusetts, the untreated ex-users had testicles about 2.3 ml smaller than non-using weightlifters, lower testosterone and lower sexual desire, and five of them still had very low testosterone 3 to 26 months after stopping.

A Danish study looked even further out. Men who had stopped on average 2.5 years earlier still had lower testosterone than controls, and 27% were below the normal range. They also reported more depressive symptoms, erectile dysfunction (27%) and low libido (40%) than either current users or non-users. Men who quit often spend months in exactly the state they were trying to avoid: low testosterone, low mood, low sex drive.

What users do about it

Gym culture has its own answer: post-cycle therapy, or PCT. Users take drugs such as hCG, which mimics LH and keeps the testicles working, or medicines that block oestrogen's feedback on the brain, to try to restart the system faster. A 2026 review describes PCT as widely used, often without any medical supervision, with limited evidence behind it: some studies suggest it speeds short-term recovery, most men recover by themselves within months anyway, and academic medicine generally does not recommend it. This page gives no doses, on purpose.

If you want kids, or just your balls back

The practical message is short. Steroids switch off the testicles' own production, and the shrinkage is the visible sign. Hormones usually return within months and sperm within about a year, but recovery is slower after long use and not guaranteed. If you are thinking about a family, by any route, sperm production is the part most at risk and the slowest to return.

See a doctor if your balls stay small, soft or sore after stopping, if your sex drive or erections do not come back, or if you are planning to have children: a blood test for LH, FSH and testosterone and a semen analysis can tell you where you stand. You do not need to have quit, or to justify anything, to ask. More on normal volumes and what they mean is in Balls.