IGF-1
Insulin-like growth factor 1 — a growth hormone mediator involved in tissue repair, muscle growth, and cellular aging.
Optimal Range
100-200 ng/mL (longevity-optimal range)
Risk-Stratified Targets
| Population / Context | Target |
|---|---|
| Longevity-optimalLower half of age-adjusted reference | 100–200 ng/mL |
| Adequate for muscle/bone maintenance | 150–250 ng/mL |
| Low (frailty/sarcopenia risk)Investigate GH deficiency if symptomatic | < 100 ng/mL |
| Elevated (accelerated aging concern)May increase cancer risk; evaluate context | > 250 ng/mL |
Why It Matters
IGF-1 exists in a complex relationship with aging. Moderate levels support muscle mass and bone density, but chronically elevated IGF-1 may accelerate cellular aging and cancer risk. The optimal range is debated in longevity medicine.
Understanding IGF-1
IGF-1 (insulin-like growth factor 1) is produced primarily by the liver in response to growth hormone (GH) stimulation and acts as the main mediator of growth hormone's effects throughout the body. It promotes cell growth, proliferation, and repair — essential for maintaining muscle mass, bone density, and tissue integrity throughout life.
The relationship between IGF-1 and longevity is one of the most debated topics in aging research. On one hand, animal studies consistently show that reduced IGF-1/GH signaling extends lifespan — from worms and flies to mice. Humans with Laron syndrome (genetic GH receptor deficiency, resulting in very low IGF-1) appear to be protected from cancer and diabetes. On the other hand, very low IGF-1 in older adults is associated with frailty, sarcopenia, cognitive decline, and increased mortality.
This apparent paradox has led to the concept of an 'optimal middle ground' — enough IGF-1 to prevent frailty and maintain function, but not so much that it accelerates cellular aging and cancer risk. Most longevity clinicians target the lower half of the age-adjusted reference range (roughly 100–200 ng/mL). IGF-1 is responsive to lifestyle: it increases with protein intake (particularly animal protein), resistance exercise, and adequate sleep, and decreases with fasting, caloric restriction, and plant-heavy diets.
Key Research
Growth Hormone Receptor Deficiency Is Associated with a Major Reduction in Pro-Aging Signaling, Cancer, and Diabetes in Humans
Guevara-Aguirre J et al. · Sci Transl Med (2011)
Key finding: Individuals with lifelong GH receptor deficiency (Laron syndrome) had extremely low IGF-1 and showed near-complete protection from cancer and diabetes despite obesity.