IGF-1 and IGF-2

IGF-1 and IGF-2, widely regarded as the most significant contributors to muscle growth, are insulin-like growth factors critical for the recovery and strength of muscle tissue damaged as a natural result of intense exercise. Their shared function is to ensure fusion between the nearby satellite cells with the damaged fibre, thereby decreasing that fibre's susceptibility to injury.

 

IGF-1 creates an insulin pulse which encourages the hypothalamus and pituitary glands to secrete GH (growth hormone), which in turn stimulates the liver to release its own IGF-1. As GH levels rise, so do levels of IGF-1. Debate still surrounds the use of IGF-1 in elite sports competitors who commonly inject it to avoid degradation by the stomach enzymes. Naturally occurring IGF-1 and IGF-2 is found in Colostrum.