Insulin-like Growth Factor 1
A hormone mainly produced by the liver, essential for childhood growth and having anabolic effects in adults. It mediates growth-promoting actions of growth hormone and is elevated during exercise and resistance training.
A hormone primarily produced by the liver that plays a crucial role in childhood growth and has anabolic effects in adults. It mediates many of the growth-promoting actions of growth hormone and is elevated during physical exercise, resistance training, and progressive muscle loading. This factor is linked to improved glucose metabolism and reduced neuroinflammatory markers in imaging studies.
What this means in real life
During puberty, rising growth hormone levels trigger the liver to release more IGF-1, which signals bones and muscles to grow faster—this is why teenagers experience growth spurts.
What it isn’t
It is not the same as growth hormone itself. While growth hormone triggers its release, IGF-1 is the actual messenger that directly stimulates cell growth in tissues; they work as a paired system, not interchangeably.
Commonly misused online
Social media often conflates IGF-1 with anabolic steroids or presents it as a standalone 'performance drug,' when in reality it's a natural hormone whose levels vary with age, nutrition, and sleep—not something athletes simply 'take' without medical supervision.