Does the amount of muscle mass you have affect your hormone balance?

Skeletal muscle is the largest tissue in your body for glucose uptake under the influence of insulin. More muscle mass therefore means more capacity to clear blood sugar, which improves your insulin sensitivity. Through this mechanism, muscle mass has a direct influence on your hormonal metabolism, even if you change nothing else about your training or diet.

Strength training temporarily raises testosterone, growth hormone and cortisol. That peak lasts an average of 15 to 30 minutes and is greatest when you train many large muscle groups simultaneously with short rest periods and high volume. People with more muscle mass can generally train heavier and mobilise more muscle mass, which influences the hormonal response. Yet multiple studies show that this acute hormone peak is not the decisive driver of long-term muscle growth, so you should not overestimate those briefly elevated values.

Strength training combined with building muscle mass also goes hand in hand with more favourable resting values of anabolic hormones: higher IGF-1 (a growth factor) and a more favourable ratio of testosterone to cortisol. These changes have been demonstrated in people who trained with creatine supplementation versus a placebo, but training and supplementation cannot be separated from each other in that research.

The reverse direction, from hormones to muscle, is better supported than the other way around. Artificially elevated testosterone clearly leads to greater muscle mass: over 20 weeks of injections, lean body mass increased by 3.4 to 7.9 kg, depending on the dose. Prolonged testosterone suppression, such as during hormone therapy, causes muscle mass and strength to decline significantly. This confirms that testosterone plays a causal role in muscle maintenance, but that says something different from the idea that your current muscle mass automatically drives up your own testosterone level.

The association does exist: more muscle mass is linked to a better insulin system and more favourable hormonal values after training, but the relationship is not one-to-one and runs largely through training itself, not through muscle mass as passive tissue. Factors such as sleep also play a role: sleep deprivation after intense exertion raises cortisol and disrupts hormone balance, regardless of how much muscle mass you have.