Insulin-like growth factor (IGF), particularly IGF-1, has been scientifically studied for its role in muscle physiology. IGF-1 is an anabolic peptide hormone structurally similar to insulin and is known to play a significant role in muscle growth, regeneration, and repair. It stimulates protein synthesis and satellite cell activation, both of which are critical for muscle hypertrophy and maintenance of muscle tone. Preclinical studies in animal models and in vitro experiments have demonstrated that IGF-1 administration can enhance muscle mass and strength, especially in conditions of muscle wasting or injury.

In human studies, IGF-1 levels have been correlated with muscle mass and function across various populations, including the elderly and those with muscle-wasting diseases. Some clinical trials and case series have explored recombinant IGF-1 therapy for conditions like muscular dystrophy and age-related sarcopenia, with mixed but occasionally promising results in improving muscle strength and tone. However, the evidence is not uniformly robust; benefits are often modest and accompanied by safety concerns such as hypoglycemia, edema, and potential proliferative effects on other tissues. As such, while IGF-1 is scientifically validated as a key factor in muscle physiology and has some evidence supporting its therapeutic use for muscle tone deficiencies, it is not widely approved for this indication outside of specific disease contexts.