HOW DO HORMONES AFFECT HOW MUCH MUSCLES GROW?

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Hormones are another component largely responsible for muscle growth and repair because of their role in regulating satellite cell activity. Insulin Growth Factor (IGF)-1, in particular Mechano-Growth Factor (MGF) and testosterone are the two most vital mechanisms that promote muscle growth.

Testosterone is the main hormone that most people think about when working out with weights, and there seems to be some validity to the thought that testosterone increases protein synthesis, inhibits protein breakdown, activates satellite cells, and stimulates other anabolic hormones. Although most testosterone is bound in the body and therefore not available to use (up to 98%), strength training seems to help not only release more testosterone, but also make the receptors of your muscle cells more sensitive to your free testosterone. Testosterone can also stimulate growth hormone responses by increasing the presence of neurotransmitters at the damaged fiber site, which can help to activate tissue growth.

The IGF regulates the amount of muscle mass growth by enhancing protein synthesis, facilitating glucose uptake, repartitioning the uptake of amino acids (the building blocks of protein) into skeletal muscles and once again, activates satellite cells to increase muscle growth.