Russia is officially barred from competition in the Olympics and other international sporting competitions for the next four years, the World Anti-Doping Agency (WADA) announced on Monday. Russia has been under close scrutiny for confirmed use of performance-enhancing drugs for several years, and was nearly banned from competition in the 2016 Olympics (instead, the International Olympic Committee cleared 278 athletes for competition and barred 111 from participating). The IOC barred Russia completely from the 2018 Olympics, but then reinstated the country’s eligibility.

WADA reports that Russian officials have been non-compliant with ongoing investigations into the country’s doping practices, which is why the ban is now extended. Russian athletes can still compete—169 of them competed at the 2018 Olympics after passing drug tests—but they will participate as neutral athletes instead of under the Russian flag.

But while Russia’s widespread doping operation and other elite sport scandals often put performance-enhancing drugs in the spotlight, it’s mostly non-Olympians—actually, mostly non-athletes—who use those drugs on a daily basis. Anabolic steroids are more popular than you might think, especially given the potential side effects. Estimates put the number of total users in the 3-4 million category, many of whom are just your average gym rats hoping to pack on the pounds more easily.

Given how widespread their use is, let’s take a minute to unpack exactly what steroids are and how they affect you.

You already have some anabolic steroids in your body

Testosterone is an anabolic steroid that your body produces naturally—no matter what your biological sex is. Though the ovaries only produce a small amount relative to the aptly-named testes, these low levels of testosterone help build muscle just the same. Steroids are a big class of chemicals that share a particular structure, which is a series of four rings. There are literally hundreds, and they perform a huge variety of biological processes. The “anabolic” part means “to build up,” so anabolic steroids are just a type of steroid that promotes protein building. There are plenty of other types of steroids that don’t have anything to do with muscle growth. Progesterone is also a steroid, but it regulates the menstrual cycle rather than promote protein production.

And we don’t just use anabolics to cheat at sports. Diseases like HIV/AIDS and cancer that cause the body to waste away can sometimes be ameliorated with steroids. The supplements can allow people to gain back some crucial muscle mass. They can also be used for kids who have extremely late-onset puberty, or adults who don’t produce enough testosterone naturally. They’re also sometimes prescribed to those experiencing gender dysphoria, in order to induce secondary sex characteristics that match the gender with which they identify.

Anabolic steroids used to be a popular way to treat other diseases, like osteoporosis, but because of their side effects they’ve fallen out of fashion in favor of better drugs.

If they’re natural, why are steroids so bad?

Plenty of people will tell you that anabolic steroids don’t pose that many risks. And of all the illicit substances people can get into, steroids aren’t the worst. But that doesn’t mean they’re safe.

Taking steroids seems like it should be straightforward. You’re just supplementing a process that your body already undergoes naturally. The problem is that your body does not operate on simple formulas, and your hormonal system does not respond well to attempts at manipulation.

Let’s take the simplest supplement as an example. Lots of people want to add a little extra testosterone to their bodies as a way of making themselves more physically masculine. And that’s tempting, because they can see how it affects the many athletes who take steroids to increase muscle mass. Those body-builders end up looking like every cinematic superhero ever, with six-packs and massive biceps. That’s because the extra testosterone is prompting their muscles to grow and heal faster, which makes putting on new muscle incredibly easy. But it also confuses their endocrine system.

When you add too much testosterone artificially, your body starts lowering production of your natural testosterone, because it thinks it’s over-producing. This is why testicles shrink on steroids—the body is shutting down hormone production there—and why fertility can drop dramatically. And confusingly, the overabundance of testosterone can actually prompt the growth of breasts. Bodies naturally convert some testosterone to estrogen. When you have a normal amount of hormones in your body, that’s not a problem. But if you jack up the T-levels, you also raise the amount of estrogen in the bloodstream. Ergo, breasts.

When you stop taking steroids, you suffer the consequences of a body that no longer thinks it has to produce testosterone naturally. Sex drive will drop, as will the ability to get an erection, and it can take years for your endocrine system to build itself back up to where it was before you started taking the drugs. Or it might not recover at all.

What other kinds of steroids do athletes use?

Most of the anabolics that athletes take aren’t just straight testosterone. We’re much better at producing synthetic steroids that don’t have such direct impacts on the endocrine system.

The Russian Olympic team was generally using a cocktail of three steroids: oxandrolone, trenbolone, and metenolone. The last two listed are pretty much strictly black-market drugs at this point, both related to testosterone and both powerful muscle-building tools. Oxandrolone isn’t quite so powerful, and is still used as a proper medication. Its effects are more specific to muscle-building as opposed to affecting secondary sex characteristics, so it can be prescribed to help patients who need to build muscle mass or heal faster. This makes it a popular choice for athletes who want the benefit of anabolic steroids without the masculinizing effects.

So are anabolic steroids really that dangerous?

Yes. As great as it would be if there were a magic pill (or shot in the butt) that could make you grow muscle with no side effects, the reality is that messing with your endocrine system is never going to be without risk. Hormones affect so many parts of your body that the side effects are wide-ranging, and when athletes take them for long periods of time they can develop serious health problems.

Let’s start with the basics: you tend to develop acne. No one wants to go back to that pubertal phase in their life. You can also experience abnormal swelling because your body retains water improperly, stretch marks because your muscles are growing too fast for your skin to keep up, and hair loss (on your head, anyway). There are spontaneous erections and nocturnal emissions. Excessive body hair, menstrual cycle disruptions, shrinking breasts, and enlarged clitorises are also common. Mood swings and extreme irritability or aggression often occur.

And on top of all those issues, which can at least fade after you stop taking the drugs, users are also more prone to kidney and liver failure. Anabolic steroids put you at higher risk for having a heart attack and developing arrhythmias, as well as contracting prostate cancer. Your immune system doesn’t function as well. Your insulin response can go haywire.

There are so many ways in which artificial steroids screw with your body, and none of them will be worth the temporary increase in muscle mass. As important as physical looks may feel right now, you won’t be checking yourself out in the mirror when you’re hospitalized after a heart attack. Be smart about your health—don’t let body image issues damage your actual body.