Is testosterone the key to building muscle after 40 — or is training more important?

The largest RCT on testosterone dose-response for muscle hypertrophy (Bhasin et al., NEJM, 1996) found that supraphysiological testosterone plus no training produced greater muscle mass and strength gains than natural testosterone plus weight training, confirming testosterone's role, but the critical finding for non-TRT men was that testosterone combined with training produced synergistic, greater-than-additive results, and that training alone produced meaningful gains at any physiological testosterone level above the hypogonadal threshold (Bhasin et al., NEJM, 1996).

For a man over 40 with testosterone in the 350–600 ng/dL range and a desire to maintain or build muscle: training is the dominant variable. Yes, testosterone facilitates muscle protein synthesis, it is an anabolic hormone. But within the physiological range, a man at 400 ng/dL who trains consistently with adequate protein will outperform a man at 600 ng/dL who does not train. The men most likely to need TRT for muscle-specific goals are those genuinely below 300 ng/dL or those who are physically active but experiencing ongoing loss of muscle mass despite adequate protein and training.

Honesty Scale: Solid (1) for the Bhasin study findings. Solid (1) for the practical superiority of training + adequate testosterone over either alone.

What to do: If your testosterone is above 350 ng/dL and you are not seeing muscle gains, examine your training and protein before pursuing TRT. Progressive overload (consistently increasing training load over months) + 1.8 g/kg protein + adequate sleep is the foundation. TRT on top of an inadequate training program will produce more side effects than muscle.

For the full picture, read The Testosterone/TRT Deep Dive