What is IGF-1?

Leo Zimmermann

Insulin-like growth factor 1 (IGF-1), sometimes called somatomedin C, is a hormone that promotes growth and prevents cell death. It is structurally similar to insulin, as well as to insulin-like growth factor 2 (IGF-2). This hormone is used across the lifespan of a human organism, but becomes most prominent during childhood and adolescence. Many animals—including mammals, birds, and fish—seem to use IGF-1 to regulate cell growth. It is produced in the liver, usually as a consequence of signals from growth hormone.

Birds and fish use IGF-1 to regulate cell growth.
Birds and fish use IGF-1 to regulate cell growth.

IGF-1 binds to two types of receptors on the outer surface of cellular membranes: the IGF-1 receptor (IGF1R) and the insulin receptor. Both of these are members of receptor tyrosine kinase (RTK) class II. The primary and unique effects of the hormone take place through IGF1R, which, when activated, triggers a chemical sequence called the AKT pathway. This process, revolving around a protein called AKT, has significant effects on the life and death of the cell. It seems this hormone has the effect of inhibiting programmed cell death. This explains its double-sided role as a stimulus to tissue growth and as an accessory to cancer.

Prostate cancer may be caused by a failure of cell death connected to IGF-1.
Prostate cancer may be caused by a failure of cell death connected to IGF-1.

A chemical resemblance to insulin also allows IGF-1 to active the insulin receptor. This protein triggers a process that ultimately causes a cell to take in more glucose from the bloodstream. IGF-1 does not bind to or activate the insulin receptor as effectively as insulin itself.

The effects of the hormone can be modulated by a series of six or seven proteins called insulin-like growth factor binding proteins (IGFBPs). IGFBP-2 and and IGFBP-5 inhibit its effects by preventing it from binding to a cellular receptor. IGFBP-3, the most common of these proteins, prolongs the life of IGF molecules.

Excess of IGF-1 and IGF1R is associated with several types of diseases. Breast and prostate cancers may be caused by a failure of cell death connected to this chemical system. Gigantism and acromegaly, which causes unnatural growth and swelling in the body, may also be connected to an excess of this molecule. Because it is correlated with growth hormone, these problems may result originally from excesses in growth hormone. Doctors suspecting these conditions may take measurements of IGF-1 for diagnostic purposes, since these usually also reflect the production of growth hormone.

Synthetic IGF-1, known as mecasermin, is used as a treatment for hormonal growth deficiency. Several different companies have attempted to create and release versions of this drug, with various levels of scientific and legal success. The hormone is also marketed as a steroid for body-building.

IGF-1 is structurally similar to insulin.
IGF-1 is structurally similar to insulin.

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Discussion Comments


@cloudel – I would definitely recommend it. When teens actually have this deficiency, it can do them so much good, both physically and psychologically.

I knew a boy in junior high who was only 4'9” tall. He looked so frail, and he wasn't developing at all.

His parents got him on an IGF-1 regimen, and he started growing. He didn't just get taller, though. His bones and muscles grew so that he looked healthy.

By the time we graduated, he was 5'9” tall! I never would have imagined that someone so tiny could grow into this.


Does anyone have an opinion on giving children the IGF-1 growth hormone? I have a good friend whose daughter is fourteen and is considering taking the hormone to help her grow. She is so short that she looks like she belongs in elementary school, and her doctor has determined that she has a growth hormone deficiency.

I just wonder if it would work. I know she desperately wants to look like the other teens.


@shell4life – I agree with you that taking IGF-1 does sound scary. I know that our bodies make it naturally, and I don't think that the amount of it we have inside is harmful. However, when we go adding more to our bodies, I think we run the risk of doing harm.

However, my brother doesn't see it this way. He takes IGF-1 for bodybuilding purposes. It has helped him beef up, because it keeps his muscle tissue from breaking down and speeds up his metabolism.

I don't think that having a perfect physique is worth the risk of getting cancer. He just doesn't think that IGF-1 could possibly cause anything bad to happen to him, since it has done him so much good.


I would be scared to use injections of the IGF-1 hormone. Some people use it to make them appear younger when they are aging, but considering the fact that it makes cells grow and keeps them from dying, it just sounds too much like a way to get cancer to me.

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