It would of course be expensive, but in theory there’s a lot to be said for combining growth hormone and IGF-1, writes the Dutch endocrinologist Joop Janssen in an article in Reviews in Endocrine Metabolic Disorders. The article is worth looking at if you’re a chemical athlete.

The first argument that Janssen comes up with is that IGF-1 remains active for longer in the body if you inject it in combination with growth hormone. This is because IGF-1 is active for longer if it is attached to the binding protein IGFBP3. If you inject IGF-1 on its own, the production of this binding protein goes down. But if you inject growth hormone and IGF-1 together, the concentration of this binding protein increases. That might mean that you would have to inject less frequently, as IGF-1 breaks down quickly in the body.

A second argument is that growth hormone makes the cells ‘ignore’ insulin. As a result, blood sugar levels rise, as does the insulin level. In the long run this might not be so beneficial to health, and it would inhibit muscle growth. If you use IGF-1 together with growth hormone, then the muscle cells become more sensitive to insulin. And that would mean more muscle protein build-up.

Why it's worth combining IGF-1 and GH

In the final section of the article, the endocrinologist stresses that there have been very few studies on the effect of combined administration of GH and IGF-1, and that his article is mainly theoretical.The advantage of combining IGF-1 and GH is also a potential disadvantage, according to Janssen. On a molecular level the same processes involved in muscle growth are also found in cancer cells and tumours. The combination of both hormones might therefore give any tumours a growth stimulus. The same applies to other side effects such as undesirable growth of the jawbone, headache and trapped nerves in the hands.

“Determination of whether coadministration of GH and IGF-I is indeed superior to GH alone or IGF-I alone awaits further study”, concludes Janssen.

Rev Endocr Metab Disord. 2009 Jun;10(2):157-62.