Understanding IGF-1: Normal vs Optimal Ranges

?What is IGF-1?

IGF-1 (insulin-like growth factor 1) is produced mainly by the liver in response to growth hormone (GH) stimulation. It is the primary mediator of growth hormone's anabolic effects — promoting muscle growth, bone formation, and cellular repair. IGF-1 levels reflect GH axis activity and nutritional status.

!Why It Matters

IGF-1 has a complex relationship with longevity — it is essential for growth and muscle maintenance but high IGF-1 may promote cellular proliferation and cancer risk. Lower-than-average IGF-1 is associated with exceptional longevity in some populations (Laron syndrome, centenarian studies). The longevity perspective suggests maintaining IGF-1 in the middle of the normal range is optimal — sufficient for muscle maintenance but not excessively anabolic.

Reference Ranges

Lab normal ranges may vary between laboratories. Optimal and longevity targets are based on research literature and should be interpreted with your physician.

Symptoms of Imbalance

• Low IGF-1: short stature in children, reduced muscle mass, osteoporosis, fatigue in adults
• High IGF-1: associated with acromegaly (enlarged hands, feet, jaw) if due to GH excess

How to Improve Your Levels

• 1Adequate protein intake raises IGF-1 (especially after periods of caloric restriction)
• 2Resistance exercise increases IGF-1
• 3Optimal sleep increases GH secretion and thus IGF-1
• 4Caloric restriction and fasting reduce IGF-1 (which may be beneficial for longevity)

When to Test

Not routinely tested. Consider in: growth concerns, suspected GH deficiency or excess, muscle wasting evaluation, or as part of a comprehensive longevity panel.

Related Biomarkers