Anabolic steroids are composed of testosterone and other substances related to testosterone that promote the growth of skeletal muscle. These substances have been in use since the 1930s to improve athletic performance and enhance aesthetics. Sometimes they are prescribed by healthcare providers to treat hormonal issues and diseases that cause muscle loss.

However, there are significant negative physical and psychological effects of using anabolic steroids.

Anabolic steroids have become widely used by bodybuilders, athletes, and others since the 1950s. But a growing awareness of steroid abuse led to federal regulation of these substances in the United States and elsewhere.

Since 1990, anabolic steroids have been classified as a scheduled III controlled substance due to growing awareness of their abuse. These drugs are legally available only with a prescription, however, they can easily be purchased illegally even online.

In the United States alone, 3 to 4 million people use anabolic-androgenic steroids. Worldwide, steroid users make up 3.3 percent of the global population.

What’s staggering is the fact that the majority of anabolic steroid users are aware of the negative effects, but continue to use them regardless. These include reduced sperm count, erectile dysfunction, baldness, breast development, and an increased risk of heart disease, stroke, and liver or kidney failure. There are also dramatic mental effects like paranoia, extreme irritability, and mania.

That’s not all. There is still much to learn about how these drugs affect the body. A new study published today in the Journal of Clinical Endocrinology & Metabolism showed how anabolic steroids harm men’s testicular function.

It’s well known that anabolic steroid abuse can cause shrunken testicles and lower testosterone levels (which leads to more steroid use to keep up) — this is known as hypogonadism.

Whether or not anabolic steroids cause long-lasting testosterone deficiency has been a matter of contention among researchers in the field. But according to the results of the study led by  Jon J. Rasmussen, a researcher at Rigshospitalet in Copenhagen, it seems like it.

“A few years ago we noted a persistent increase in the referral of men with hypogonadism due to previous use of anabolic steroids and this prompted us to perform the study. The main finding is that illicit use of anabolic steroids seems to cause a persistent impairment of Leydig cells in the testicles which is the major source of testosterone in men,” Rasmussen told ZME Science.

The study involved 132 participants, who were originally recruited for another study and whose ages ranged from 18 to 50. The participants were split into three roughly equal groups: men who currently use anabolic steroids, former steroid users, and those who never used steroids. Former users reported not taking anabolic steroids for the past 32 months on average.

The researchers zoomed in on a hormone made by the Leydig cells in the testicles, which are responsible for making testosterone. This marker, known as serum insulin-like factor 3 (INSL3), is a more reliable indicator of testicular function than testosterone, whose levels can vary greatly during the day.

Among current steroid users, INSL3 was heavily suppressed compared with former users and never-users. But compared to never-users, former steroid users had significantly lower INSL3 concentrations: 0.39 versus 0.59 micrograms per liter.

This suggests that the effect of anabolic steroids on testicular function can persist for many years after cessation. The longer the duration that men reportedly used steroids, the lower their INSL3 levels were.

“The study adds to the existing literature on the subject that illicit use of anabolic steroids can cause a persistent impairment of the gonadal function in men,” Rasmussen said in an email.

The findings are due to be presented at ENDO 2021, the Endocrine Society’s annual meeting, which runs from March 20-23.