Does growth hormone make your muscles bigger?

Short answer

No. Lean mass went up by 2.1 kg, but the gain was mostly water, and strength did not improve. Swelling and joint pain went up instead.

Does growth hormone make your muscles bigger?
'Growth hormone → more muscle → more strength' — does this formula hold?
Because of its name, growth hormone is known as a muscle-building drug. We used randomized trials to check how body weight, muscle and strength actually changed in people who took it.
Body weight did go up
Lean mass up 2.1 kg
In a set of 27 randomized trials, 303 people took growth hormone for 20 days on average. Lean mass (muscle and everything except fat) rose 2.1 kg more than in those who did not. So far, the formula seems to hold.
But strength did not go up
Neither strength nor endurance changed
An analysis that pooled 11 trials (254 people) found growth hormone cut fat and raised lean mass, but weeks to months of use did not change strength or maximum oxygen uptake (endurance).
The gain was water, not muscle
Water outside the cells went up
In a trial where 96 people took it for 8 weeks, lean mass rose, but the rise came from more water outside the cells. Fat went down. Weight that looked like muscle was actually water held in the body.
Same story with strength training
Muscle size and strength did not grow more
16 people did the same strength training for 12 weeks while taking growth hormone or a fake drug. The growth hormone group gained more lean mass and body water, but thigh muscle protein building, limb size and strength did not rise more. A 16-week trial in 23 people found the same.
The only gain was short sprints
9%, gone 6 weeks after stopping
In the 96-person trial, growth hormone raised short sprint capacity by 3.9%, and by 8.3% in men who also took testosterone. Strength (deadlift), jumping and endurance did not change. Even the sprint gain was gone 6 weeks after stopping.
The cost: swelling and joint pain
The body swelled with the extra water
In the 303-person analysis, the growth hormone group had swelling and fatigue more often. In 220 people (average age 69) who took it for 27 weeks on average, swelling, joint pain, wrist numbness (carpal tunnel syndrome) and breast growth in men were more common. A 2024 overview listed the same risks.
Summary: weight goes up, muscle and strength don't
The formula breaks at 'more muscle'
Growth hormone raised lean mass by 2.1 kg, but it was mostly water. Even with strength training, muscle size and strength did not grow more. The only gain was 3.9% in short sprints, while side effects such as swelling and joint pain went up.