Which hormone is primarily responsible for muscle growth?

Testosterone is a key hormone in the process of muscle growth, also known as hypertrophy. It plays a significant role in promoting protein synthesis, which is essential for building and repairing muscle tissues. This hormone enhances the body’s ability to utilize amino acids effectively, thus facilitating the growth of muscle fibers in response to resistance training and other forms of physical exertion.

Additionally, testosterone influences various physiological factors that contribute to muscle development, such as increasing red blood cell production, which improves oxygen delivery to muscles during exercise, and helping to reduce fat mass, allowing for a greater ratio of lean muscle. It also impacts the activity of satellite cells, which are crucial for muscle repair and growth following injury or stress from workouts.

Other hormones like cortisol, insulin, and estrogen play different roles in the body but are not primarily associated with muscle growth in the same way as testosterone. Cortisol is often associated with stress response and can lead to muscle catabolism if levels are excessively high over long periods. Insulin is essential for nutrient uptake but does not directly stimulate muscle growth. Estrogen, while playing a role in various bodily functions, including fat distribution and reproductive health, is not the main driver of muscle hypertrophy. Thus, testosterone's direct impact on muscle