We analyzed the available evidence and found that turning off myostatin after birth in mice is linked to increased muscle growth. Specifically, one assertion shows that when the myostatin gene is switched off only in the muscles of mice after they are born, their muscles grow just as large as when the gene was turned off from the very beginning of life [1]. This suggests that myostatin continues to play a role in limiting muscle size even after development is complete. What we’ve found so far is based on a single assertion supported by six studies or observations, with no studies contradicting this finding. The evidence we’ve reviewed leans toward the idea that myostatin doesn’t just shape muscle growth during early development—it also holds back muscle growth later in life. This doesn’t mean turning off myostatin will have the same effect in humans, or that it’s safe or practical to do so. It simply shows that, in mice, the biological brake on muscle growth remains active after birth and can be released even then. Our current analysis shows this effect is consistent across the data we’ve reviewed, but we only have one formal assertion to work from. More studies would help clarify whether this holds true under different conditions, such as varying ages, diets, or levels of physical activity. For now, if you’re curious about muscle growth in mice, the evidence suggests that blocking myostatin after birth still leads to bigger muscles—not because of early development, but because the gene keeps working even after birth.