IGF-1 (Insulin-Like Growth Factor 1): What Your Result Means

What is IGF-1 (Insulin-Like Growth Factor 1)?

Growth hormone is released in brief pulses, so measuring it directly is unreliable — that is why doctors measure IGF-1 instead. IGF-1 is produced by the liver in response to growth hormone and reflects its average effect over time. It drives growth in children and tissue maintenance in adults, and it is the key marker for evaluating growth-hormone disorders.

Typical reference interval: IGF-1 follows strict age curves — high in childhood, peaking in puberty, then declining through adult life. Ranges are wide (commonly roughly 100–300 ng/mL in middle-aged adults, higher in youth); laboratories report age- and sex-matched reference values, which are essential for interpretation.. Laboratories differ — the interval printed on YOUR report always governs.

If your IGF-1 (Insulin-Like Growth Factor 1) is high

Common reasons IGF-1 (Insulin-Like Growth Factor 1) runs above the reference interval:

• Growth-hormone excess (acromegaly) — too much growth hormone from a pituitary tumor raises IGF-1 steadily — the classic high-IGF-1 story in adults
• Puberty and growth spurts — expected physiological peaks in the young
• Pregnancy — IGF-1 rises naturally
• Growth hormone supplementation — using growth hormone for any reason raises measured IGF-1

If your IGF-1 (Insulin-Like Growth Factor 1) is low

Common reasons IGF-1 (Insulin-Like Growth Factor 1) runs below the reference interval:

• Growth-hormone deficiency — a pituitary that releases too little growth hormone produces low IGF-1
• Malnutrition or very low calorie intake — the liver makes less IGF-1 when fuel is scarce — a starvation signal
• Liver disease — a damaged liver produces less IGF-1
• Advanced age — IGF-1 naturally trends downward after middle age
• Chronic illness — prolonged disease suppresses the growth-hormone axis

Symptoms worth knowing

IGF-1 causes no symptoms itself. High levels are associated with enlarged hands and feet, coarsened facial features, and joint or heart issues when driven by growth-hormone excess; low levels in children show as slowed height gain, and in adults as reduced muscle and energy. Testing is about the axis, not the molecule.

What usually happens next

1. A high IGF-1 in an adult warrants a medical review for growth-hormone excess — imaging of the pituitary is the usual next step
2. A low IGF-1 in a child with slow growth calls for pediatric endocrine evaluation
3. In adults, low IGF-1 is interpreted with age, nutrition, and liver health before any intervention

Frequently asked questions about IGF-1 (Insulin-Like Growth Factor 1) results