American scientists have identified a potential link between testosterone replacement therapy (TRT) and an increased risk of atrial fibrillation, a dangerous heart rhythm problem that can lead to stroke. The findings, published by researchers at the Kansas City Veterans Affairs Medical Center, suggest that maintaining testosterone levels within a narrow, normal range is crucial for heart health.
Atrial fibrillation causes the heart to beat irregularly, which can result in heart failure and stroke. The new research reviewed existing studies and found that men with very high or abnormally low testosterone levels face a greater risk of developing this condition. Conversely, men with testosterone levels in the middle of the normal range appear to be at the lowest risk.
Testosterone therapy is typically prescribed to men with hypogonadism, a condition where the body does not produce enough of the primary male sex hormone. While testosterone levels naturally decline with age, only a small percentage of men experience a clinical deficiency. Low levels can cause fatigue, mood disturbances, and reduced libido.
However, TRT has gained popularity in recent years among men without a diagnosed deficiency, with claims of boosted energy and improved athletic performance. This has led some men to seek private treatments, which may not adhere to the same strict criteria as publicly funded healthcare systems. Experts have previously cautioned against non-medically indicated use of TRT, citing side effects such as weight gain and prostate enlargement.
"Both too little and too much testosterone appear to raise the risk of atrial fibrillation... which means the dose and the target level matter," said study co-author Rajat Barua, chief of interventional cardiology at Kansas City VA Medical Center. "What the review argues is that treatment should be individualised and monitored."
The way TRT is administered can significantly impact testosterone level fluctuations. Testosterone gels are absorbed gradually, while injections can initially cause sharp spikes followed by declines before the next dose. Longer-acting injections, administered every 10 to 14 weeks, offer more stable levels and might be preferable for men at higher risk of heart rhythm problems.
Researchers suggest that before starting TRT, doctors should assess patients for atrial fibrillation risk factors, including obesity, sleep apnea, high blood pressure, and alcohol consumption. Regular monitoring of heart rhythm and blood pressure is also recommended to ensure treatment safety. The study's authors emphasized that their conclusions are based on a review of existing evidence and are open to interpretation.