Hormones and muscle growth: do they matter

Do circulating hormones matter for muscle growth? 💪

Certain hormones are associated with cell growth, so called “anabolic hormones”. These include testosterone (T), growth hormone (GH), IGF-1 and many others. In the muscle world this has created the dogma that anabolic hormones are main drivers of the growth response to exercise.

However, is there actually direct evidence for circulating hormones to regulate changes in muscle size🤔? The following study looked at exactly that question [see picture for reference of study]:

- 56 young men with no recent weightlifting experience

- 5 whole body resistance exercise sessions per week

- Total duration of 12 weeks

- Lean body mass (LBM), cross sectional area (CSA) and strength were assessed before and after the 12 weeks

- Circulating hormone levels were measured after one of the training sessions

The results are in the picture above📃:

R-values indicate how well one variable correlates with another. The closer this value gets to 1.0 the better. An r-value of 0.14 for Testosterone and LBM is not very impressive. It means some of the individuals with the lowest T levels after exercise showed the biggest increases in LBM after 12 weeks.

Therefore, circulating levels of anabolic hormones seem to be very poor predictors of muscle growth. Interestingly, the catabolic “stress hormone” Cortisol correlated better with changes in LBM than the anabolic hormones. Maybe “stress” is reflecting intensity?

Check the paper for details: PMID: 22105707

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