People who use anabolic steroids, that mimic testosterone's effects in the human body, may increase the underlying risk of a heart condition called atrial fibrillation, a new study has found.

The new research, published in the Journal of Physiology, found that male sex hormones, such as testosterone, also called androgenic anabolic steroids (AAS), are misused for muscle building, particularly among young men.

This can increase the risk of atrial fibrillation in individuals genetically predisposed to heart diseases.

"Our study can significantly contribute to understanding the impact on the heart health of young men who misuse anabolic steroids to increase muscle mass," said lead author Dr Laura Sommerfeld, postdoctoral researcher from the University of Birmingham, UK.

"Recent reports have shown that young men, in particular, are being targeted on social media such as TikTok being sold testosterone products, but we have shown how the misuse of steroids carries a specific risk that many people will not be aware of," she added.

The scientists examined potential effects on a condition called arrhythmogenic right ventricular cardiomyopathy (ARVC), which is genetically determined and primarily attributed to disruptions in the formation of cell connections critical for heart muscle stability.

"Heart muscle diseases like ARVC affect young, athletic individuals and can lead to life-threatening heart rhythm disturbances. Atrial fibrillation is a common condition in the general population. Elevated testosterone levels can result in an earlier onset of these diseases," said Professor Larissa Fabritz, from the varsity.

The scientists initially confirmed, based on clinical patient data, that ARVC occurs more frequently and severely in men than in women.

In laboratory experiments, they discovered that six weeks of AAS intake, combined with impaired cell connections, could lead to reduced sodium channel function in heart tissue and a slowing of signal conduction within the atria.

"This work implies that young male individuals with key inherited genetic changes have a greater risk of developing electrical problems in the heart in response to anabolic steroid abuse," said Dr Andrew Holmes, co-author and Assistant Professor in the Institute of Clinical Sciences at the University of Birmingham.