New Gene Release: IGF1 and IGF1_2

Thursday, March 17, 2016. Author Alex Auld

The Role of IGF1

For anyone looking to build muscle mass and strength, circulating levels of IGF1 can play a pivotal role. IGF1 (or Insulin-like Growth Factor 1), is a hormone coded by the IGF1 gene. IGF1 acts on many downstream growth factors and hormones, promoting cell growth and proliferation (cell division). Interestingly, IGF1 also regulates growth hormone (GH), and stimulates the production of Nitric Oxide (NO). By means of vasodilation (widening of the blood vessels) NO aids the delivery of essential nutrients and, importantly, transport of waste products that are produced when exercising. A good blood flow is also important for recovery.

Due to its function in muscle growth, high levels of IGF1 have been associated with increased baseline strength and response to resistance exercise, which is an advantage for power based sports and activity.

In addition to your IGF1 and IFG1_2 results, there are environmental factors that can affect your IGF1 levels. As we age, there is a natural decline in IGF1 production, which can onset sarcopenia (loss of skeletal muscle and strength). Following a caloric restricted diet can also decrease IGF1 levels, whilst a high protein diet can be beneficial for those with lower circulating levels of IGF1.

IGF1 and Genetics

As mentioned above, circulating levels of IGF1 are influenced by the gene that regulates its production. Although gene results for both IGF1 and IGF1_2 have been released, they should not be thought of as different genes. They are variations in the same gene, which produces the same protein, and have a slightly different effect on the protein’s levels and function, and ultimately on the physical trait.

Whilst IGF1 is associated with muscle growth and strength gains, IGF1_2 impacts your maximal force output. Therefore both are indicators of speed/power performance.

So which are the variations that can claim this muscle and strength building advantage?


Of the three variations (AA, AG and GG), it is AA that has been associated with higher circulating levels of IGF1 protein.

This variation is commonly found in strength athlete populations. Carriers of the AG variation have shown to have higher levels of IGF1 protein than GG carriers, who have been observed as having ‘average’ levels of IGF1.


Although part of the same gene, the variations of IGF1_2 are found in a different part of the gene and are coded by different alleles – TT, TC and CC. The advantageous variation is CC, as this is the one associated with higher maximal force production. However, less than 10% of the global population carry it!

The TT variation is associated with the lowest maximal force output, whilst TC is intermediate between the two.

Although your genetic variations are an indicator of your potential muscle mass, strength and maximal force, they are by no means the only contributing factor. Resistance based training will increase all of these, especially when you follow your personalised FitnessGenes recommendations.

Your IGF1 and IGF1_2 result

So do you carry one, or even both variations that may give you the athletic edge? Discover your individual results and further functions of IGF1 protein by logging into your FitnessGenes account.

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