IGF-1 explained: growth hormone, muscle growth and the longevity trade-off

In the biohacking corner, IGF-1 is happily sold as the muscle-growth button: the higher, the better. But anyone who looks beyond the next training block runs into an uncomfortable nuance. IGF-1 drives growth and recovery, and those very growth signals carry a trade-off for how you age over the long term.

My stance: with IGF-1, more is not automatically better. Both a very low and a very high level are linked to unfavourable outcomes, which makes this a marker to read with nuance, not to push up artificially.

What IGF-1 is and does

IGF-1 stands for insulin-like growth factor 1. Your liver produces it under the influence of growth hormone, and it is a key link in muscle growth, tissue repair and bone building. When you train, eat and sleep to get stronger, IGF-1 works in the background. A healthy level therefore belongs to a body that recovers well.

Your IGF-1 value declines gradually with age. That is normal and not immediately something to correct.

The trade-off for longevity

Here it gets interesting. In longevity research, a moderate IGF-1 appears more favourable than an extremely high level. The biology behind this is called antagonistic pleiotropy: the same growth signals that make you stronger now can, at older age, drive cell division and growth processes that you would then rather slow down (Gubbi, 2021).

Large cohort studies show a U-shaped relationship: both a low and a high IGF-1 are linked to higher long-term mortality, while the middle range appears most favourable (Sanders, 2018; Burgers, 2022). The table below sums up the trade-off.

What this means for you as an athlete

For the healthy, naturally training athlete, this is mainly a reason not to push your IGF-1 up artificially. Training, enough protein and good sleep keep your value in a healthy range without seeking out the longevity trade-off. The WHO stresses that regular physical activity is one of the most strongly supported factors for healthy ageing, and that fits exactly with a moderate, stable IGF-1.

If you use growth hormone or peptides, that is a different story: then you actively drive IGF-1 up, and it is wise to track the marker and weigh it up with a doctor. The Dutch Health Council (Gezondheidsraad) also points out that hormonal interventions in healthy people often do not have a proven benefit.

What raises and lowers your IGF-1 naturally

Your IGF-1 is mostly determined by your growth hormone, your age and your nutritional status. Enough protein and a healthy energy intake keep your value up, while prolonged severe under-eating can lower your IGF-1. Strength training and good sleep support a healthy level, because most growth hormone release happens during deep sleep. That is the nice part: the lifestyle that makes you stronger keeps your IGF-1 in a healthy range by itself.

In the other direction, age and artificial interventions play a role. As you get older, IGF-1 declines gradually, which is normal. Growth hormone and certain peptides push the value up, and that is exactly where the trade-off sits: you may gain some anabolic signal, but you seek out the longevity downside. For a healthy athlete, that rarely works out in your favour.

How to test your IGF-1

IGF-1 is relatively stable across the day, so you do not have to draw at a specific time, but do test on a calm day. Judge your IGF-1 in relation to your total testosterone and your recovery markers for a complete hormonal picture. Our general hormones test is a logical start for that.

Read on: the pillar blood values for strength athletes, plus peptides explained and testosterone and muscle mass.

My advice: do not aim for the highest possible IGF-1. Keep your value in a healthy range with training, nutrition and sleep, and discuss a strikingly high or low result with your doctor.

References

1. Sanders JL, Guo W, O'Meara ES, et al. Trajectories of IGF-I predict mortality in older adults: the Cardiovascular Health Study. The Journals of Gerontology: Series A. 2018. PMID: 28977343.
2. Gubbi S, Schwartz E, Crispim CA, et al. The antagonistic pleiotropy of insulin-like growth factor 1. Aging Cell. 2021. PMID: 34363732.
3. Burgers AMG, et al. Association between IGF-1 levels ranges and all-cause mortality: a meta-analysis. Aging Cell. 2022. PMID: 35048526.
4. WHO and the Dutch Health Council (Gezondheidsraad), public information on physical activity, healthy ageing and hormonal interventions.

Disclaimer

Every blood test result includes a professional assessment by a BIG-registered doctor. This article gives general information and is not a substitute for medical advice. A blood test is a tool to walk into the conversation with your GP better informed, not a diagnosis in itself. For treatment decisions, discuss your results with your GP.