Testosterone, the primary male sex hormone, plays a key role in sexual desire and erectile function. Low testosterone (low T) levels can contribute to ED, particularly if accompanied by fatigue, reduced libido, and mood changes. However, not all cases of ED are due to low testosterone. Blood tests can determine hormone levels, and if low T is diagnosed, testosterone replacement therapy (TRT) may be an option. It’s important to work with a doctor to evaluate if TRT is safe and beneficial in your case.