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IGF-1 Optimal Reference Ranges

Written by Tommy Wood MD, PhD

June 11, 2017

We know that the normal range your laboratory gives you for a specific blood marker doesn’t necessarily imply what’s truly optimal. Based on this paper showing the U-shaped curve of IGF-1 levels and mortality, and age-specific IGF-1 “normal” ranges from the Mayo Clinic laboratories, I have created something close to an “optimal” range for IGF-1 (see table below). I did this by taking the average (mean) of the normal range, then including just ½ of a standard deviation either side. This will cover the 38% of people either side of average, and captures the region where the error margin suggests a measured IGF-1 level is associated with the lowest mortality rate. As the truly lowest mortality rate is in those with the 55th percentile of IGF-1 level (i.e. just above average), being in the upper half of our optimal range may be a bit better. However, if you’re worrying intensely about your IGF-1 level and it’s within the range below, we think there are probably other things you can optimise that will be more impactful. Like closing the computer and going for a walk.