What Is IGF-1?
Insulin-like growth factor 1 (IGF-1) is produced mainly by the liver in response to growth hormone (GH). Because GH is released in unpredictable pulses, IGF-1 — which has a stable level throughout the day — is used as a reliable measure of overall growth hormone activity.
Normal IGF-1 Levels by Age
| Age | Normal Range (ng/mL) |
|---|---|
| 0–2 years | 31–160 |
| 3–7 years | 16–288 |
| 8–14 years | 90–507 |
| 15–19 years | 217–524 |
| 20–29 years | 127–424 |
| 30–39 years | 115–307 |
| 40–49 years | 94–269 |
| 50–59 years | 87–225 |
| 60+ years | 55–186 |
Causes of High IGF-1
- Acromegaly — excess growth hormone in adults (causes enlarged hands, feet, features)
- Gigantism — excess GH before growth plates close in children
- Obesity (can mildly raise IGF-1)
Causes of Low IGF-1
- Growth hormone deficiency (children: stunted growth; adults: fatigue, reduced muscle mass)
- Malnutrition or eating disorders
- Liver disease (liver makes IGF-1)
- Hypothyroidism
- Chronic illness
IGF-1 and Acromegaly
The definitive screening test for acromegaly is IGF-1. If elevated, it is confirmed by oral glucose suppression test (GH should suppress but doesn't in acromegaly).
FAQs
Should IGF-1 be tested on an empty stomach?
IGF-1 levels are relatively stable and do not require fasting, though some labs may request it.
Can athletes have high IGF-1?
Intense exercise slightly raises GH and IGF-1 but rarely to pathological levels without exogenous GH.
Is low IGF-1 treatable?
Yes — GH deficiency can be treated with daily GH injections after confirming the diagnosis.
Medical Disclaimer: IGF-1 results must be interpreted alongside growth hormone stimulation tests and clinical findings by an endocrinologist.