Michael West discusses growth hormone supplementation: the risks associated with the signaling protein IGF-1 change with age
Michael West discusses growth hormone supplementation: the risks associated with the signaling protein IGF-1 change with age
On September 2, aging researcher Michael West raised the question of growth hormone and IGF-1 supplementation. His post was prompted by an observational analysis of 440 185 participants in UK Biobank, a health database. Baseline blood IGF-1 levels were associated with subsequent disease and death in a U-shaped pattern that varied with age.
Growth hormone exerts some of its effects through insulin-like growth factor 1 (IGF-1), a protein involved in tissue growth and development. In his post, West asks:
“Do growth hormone and IGF-1 supplements slow, reverse, or accelerate aging?”
West argues that growth hormone and IGF-1 supplementation accelerates the overall aging process.
The authors of a 2021 paper examined a conflict in earlier observational findings. Higher IGF-1 was associated with better outcomes in younger groups and worse outcomes in older groups. They tested whether age changed the direction of this association. They measured IGF-1 at baseline, compared these levels with subsequent disease and death, and then repeated the analysis within age groups.
The associations with mortality, dementia, diabetes, vascular disease, and osteoporosis were U-shaped. People with the lowest and highest IGF-1 levels had a greater risk of these outcomes than people with levels near the middle of the range. Cancer followed a different pattern. Higher IGF-1 was generally associated with a higher incidence of new cases. In younger groups, higher IGF-1 was associated with a lower risk of several outcomes. This association weakened with age, and high levels became associated with unfavorable results for several outcomes.
In an experiment in old mice, IGF-1 from young blood helped restore the protective barrier between the blood and brain tissue. In that experiment, the researchers altered signaling in a specific tissue. By contrast, the UK Biobank study measured naturally occurring IGF-1 levels in humans and then examined their association with diseases and deaths that occurred later.
The paper’s authors interpreted this pattern in terms of antagonistic pleiotropy. A biological trait may support growth and development early in life but become associated with disease later. West discusses growth hormone supplementation in relation to age, baseline IGF-1 levels, and the specific function that the intervention is intended to enhance.