Why it’s worth combining IGF-1 and GH

It would of course be expensive, but in theory there’s a lot to be said for combining growth hormone [structure shown below] 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.

Human Growth Hormone

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.


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.

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

Advantages and disadvantages of GH/IGF-I combination treatment.


Growth hormone (GH) is the primary regulator of insulin-like growth factor-I (IGF-I) production in a wide variety of tissues. There is much overlap in the endocrine, metabolic and anabolic effects of GH and IGF-I but both hormones have divergent effects on glucose metabolism, insulin sensitivity and differentiation of prechondrocytes. Theoretically combined administration of GH and IGF-I may be more effective than GH alone or IGF-I alone. Arguments in favor for this are: 1] Clearance of IGF-I may be markedly altered by the co-administration of GH and this will provide sustained actions of IGF-I. 2] Higher serum IGF-I levels are achieved with a combination treatment of GH and IGF-I than with GH treatment alone or IGF-I alone. In addition, combination therapy may have additive or synergistic effects. 3] The combination GH and IGF-I counteracts disadvantageous effects on glucose metabolism of either GH alone or IGF-I alone. 4] GH may exert direct actions on tissues independently from IGF-I. 5] Combination of GH and IGF-I may be more effective in improving tissue IGF-I levels. The combination therapy of GH and IGF-I might be beneficial in growth retardation, in certain specific subgroups of critically ill or catabolic patients and in the treatment of GH-deficient subjects with the metabolic syndrome and/or manifest diabetes. It is at present unknown whether an optimal balance between safety and efficacy can be achieved with the combination therapy of GH and IGF-I, since this combination has been evaluated in only a small number of patient populations and in studies of a relatively short duration. In addition, a disadvantage may be the financial costs of combination therapy of GH and IGF-I. In conclusion, there are many reasons for believing that administration of the combination therapy of GH and IGF-I could have advantages above GH alone or IGF-I alone. However, determination of whether co-administration of GH and IGF-I indeed is superior to either agent alone awaits further study.

PMID: 18604645 [PubMed – indexed for MEDLINE]

Source: http://www.ncbi.nlm.nih.gov/pubmed/18604645