IGF-1: What the Research Actually Shows

IGF-1 (insulin-like growth factor 1) is a growth factor the body makes, mostly in the liver in response to growth hormone. It is one of the most studied molecules in growth and muscle biology, so this page lays out what researchers actually looked at, in plain words, with links you can check yourself.

What researchers have studied

Growth in children with a specific deficiency (Chernausek, Journal of Clinical Endocrinology and Metabolism, 2007). A long-term human trial gave recombinant human IGF-1 to children who could not make enough of their own, because of a genetic problem in the growth hormone pathway. Researchers observed faster height growth, strongest in the first year of treatment. This was a deficiency model, not a study of healthy or trained adults. PMID 17192294. https://pubmed.ncbi.nlm.nih.gov/17192294/

Longer follow-up in the same condition (Backeljauw, Journal of Clinical Endocrinology and Metabolism, 2001). Eight children with the same growth hormone insensitivity syndrome received recombinant IGF-1 for six to seven years. Growth velocity jumped in the first year (about 9 cm per year versus 4 at baseline) and then tapered off over time. Again, a deficiency population, not healthy adults. PMID 11297575. https://pubmed.ncbi.nlm.nih.gov/11297575/

Muscle size in mice, by age (Barton, Journal of Applied Physiology, 2006). Researchers used a virus to add extra IGF-1 into mouse leg muscle. Two forms of IGF-1 both grew muscle in young mice, but only one still worked in older mice. What researchers drew from it was that age changes how muscle responds to IGF-1. Mouse model, not people. PMID 16439513. https://pubmed.ncbi.nlm.nih.gov/16439513/

IGF-1 forms and aging muscle (Ascenzi, Aging Cell, 2019). Using mice bred to carry extra IGF-1, researchers found one form drove more muscle growth in young animals, while both forms helped older animals hold onto muscle mass and strength. They tied the effect to cell cleanup pathways. Still a mouse model. PMID 30953403. https://pubmed.ncbi.nlm.nih.gov/30953403/

How the signal works, reviewed (Yoshida and Delafontaine, Cells, 2020). A review paper pulled together the lab work on how IGF-1 tells muscle to build and how it blocks muscle breakdown. It maps the main build pathway (PI3K/Akt/mTOR) and the brakes IGF-1 puts on wasting signals. It is a summary of animal and cell research, not a human outcome study. PMID 32858949. https://pubmed.ncbi.nlm.nih.gov/32858949/

How it works

The setup is the growth hormone axis. Your pituitary gland releases growth hormone. That signal reaches the liver and other tissues, and they answer by making IGF-1.

IGF-1 then binds its own receptor (called IGF-1R) on the surface of cells. In muscle research, that binding switches on the PI3K/Akt/mTOR pathway, which is the main signal for building new protein and for waking up satellite cells (the repair cells that sit next to muscle fibers). In the same lab work, IGF-1 also quiets the signals that break muscle down.

One more piece matters. In the blood, most IGF-1 does not float free. It rides on carrier proteins called IGF binding proteins, and those carriers control how much IGF-1 is actually free to act. That detail becomes important with the LR3 analog, which is covered on its own page.

What the research does not establish

• Most of the muscle data is mice or isolated cells, not healthy humans.
• The human trials were in children with a specific genetic deficiency, and they measured height.
• Nothing here is a safety conclusion. This is not a claim that the compound is safe to use.
• Outside the specific deficiency condition studied, there is no approved human use.

For Research Use Only. Not for human consumption. Etched Research supplies compounds for laboratory and research use only. Independent lab results, where they exist, are published on the COA page. Nothing on this page is medical advice, a health claim, or a recommendation to use.