IGF-1
Insulin-like growth factor – marker for the GH axis and biological aging
Also known as
Definition
Insulin-like growth factor 1 (IGF-1, formerly somatomedin C) is produced mainly in the liver in response to growth hormone (GH). IGF-1 mediates the anabolic effects of GH on muscles, bone, and organs. Levels are strongly age-dependent (peak in puberty, steady decline from age 30) and serve as a marker of GH/IGF-1 axis activity.
| Parameter | Value |
|---|---|
| Unit | nmol/l (ng/ml) |
| Reference Range | Strongly age-dependent. Adults 30–40 yr: 15–40 nmol/l (115–307 ng/ml) | 50–60 yr: 10–28 nmol/l (77–215 ng/ml). Always interpret against age-adjusted SDS score. |
| Optimal Range (lab2go) | Age-adjusted value in the upper third of reference range (SDS 0 to +1) (lab2go Optimum Zone — values in the lowest quartile associated with frailty and mortality) |
Conversion: 1 nmol/l = 7.65 ng/ml. US labs report in ng/ml (strongly age-dependent; e.g., 40-year-old man: ~90–250 ng/ml).
↓ What a low value means
Low IGF-1 suggests growth hormone deficiency (pituitary insufficiency), severe liver disease (site of IGF-1 synthesis), malnutrition, chronic inflammation, or marked dietary restriction (fasting). Associated with: muscle wasting (sarcopenia), bone density loss, increased fracture risk, fatigue, and cardiovascular risk.
↑ What a high value means
Elevated IGF-1 (> 2 SDS above age median) occurs with acromegaly (GH-secreting pituitary tumor) or excessive GH/IGF-1 supplementation. Chronically high IGF-1 levels are epidemiologically associated with increased risk of breast, prostate, and colorectal cancer.
✓ How to optimize this marker
Diet: higher protein intake (1.6–2.0 g/kg/day) and dairy products raise IGF-1. Intermittent fasting lowers IGF-1 (also a pro-longevity effect). Resistance training is the strongest non-pharmacological stimulator of the GH/IGF-1 axis. Sleep (deep sleep phases): GH is released pulsatilely at night.
When to test
As a marker of GH axis activity, acromegaly screening, anti-aging diagnostics from age 40, suspected sarcopenia, pituitary disease, or to monitor GH therapy. Always interpret against an age-corrected reference range.
Frequently asked questions
Is a high IGF-1 level good or bad for longevity? +
It is complex. Short to medium term, IGF-1 supports muscle preservation and physical capacity. Chronically elevated levels (top quartile) are associated with increased cancer risk in epidemiological studies. Centenarian studies (longevity research) sometimes show lower IGF-1 in the oldest old. The optimal balance appears to lie in the age-corrected mid-range.
Can I influence IGF-1 through diet? +
Yes. Milk products, animal protein, and total calorie intake raise IGF-1. A plant-based diet and caloric restriction lower IGF-1 (EPIC study). Intermittent fasting (> 24 hours) significantly lowers IGF-1. Resistance training transiently raises IGF-1 pulsatilely through GH release.
What is the difference between IGF-1 and growth hormone (GH)? +
GH is released pulsatilely from the pituitary (half-life ~20 min) and is difficult to measure reliably in blood. IGF-1 is produced in the liver as a stable response to GH (half-life ~12–15 hours) and reflects average GH activity over the preceding hours to days. IGF-1 is therefore the better clinical marker for the GH axis.
How does sleep affect IGF-1 levels? +
Growth hormone is released mainly during the first sleep cycles in deep sleep (NREM sleep) — ~80% of daily GH production occurs during the night. Sleep deprivation significantly reduces GH pulses and, over time, also lowers IGF-1. Regular sleep before 11 PM optimizes the GH axis.
Sources
- Le Roith D (2003) Clinical review: the roles of insulin-like growth factors in the adult organism. J Clin Endocrinol Metab.
- Kaplan SA, Cohen P (2007) The somatomedin hypothesis 2007. J Clin Endocrinol Metab.
- Pollak M (2012) The insulin and insulin-like growth factor receptor family in neoplasia. Nat Rev Cancer.
Last Reviewed: May 28, 2026 · sina
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.