Your Growth and Repair Signal
IGF-1 is produced by your liver in response to growth hormone (GH). While GH spikes and disappears quickly, IGF-1 is the stable downstream signal that actually does most of the work: building muscle, strengthening bones, repairing tissues, and supporting brain health. It's the best blood marker for growth hormone status because GH itself is too pulsatile to measure reliably.
What is IGF-1 (Insulin-like Growth Factor 1)?
IGF-1 is a peptide hormone produced primarily by the liver in response to growth hormone stimulation. Unlike GH (pulsatile, peaks during sleep), IGF-1 is stable throughout the day, making it the preferred marker for assessing GH axis function. IGF-1 declines naturally with age.
↑ What High IGF-1 (Insulin-like Growth Factor 1) Means
Excess growth signaling. Can indicate acromegaly (GH-producing pituitary tumor) or high-dose GH supplementation. Chronically high IGF-1 is associated with increased cancer risk (growth signals that promote tissue repair also promote tumor growth).
Common symptoms:
Acromegaly: enlarged hands/feet, coarsened facial features, jaw growth · Joint pain · Headaches · Sleep apnea · Excessive sweating
↓ What Low IGF-1 (Insulin-like Growth Factor 1) Means
Insufficient growth and repair. Causes: GH deficiency, malnutrition, liver disease, chronic illness, or aging. Low IGF-1 means reduced muscle building, poor tissue repair, and accelerated aging.
Common symptoms:
Fatigue and low energy · Decreased muscle mass · Increased body fat (especially abdominal) · Poor exercise recovery · Reduced bone density · Thin skin · Cognitive decline · Depression
Why It Matters
When normal:
Best stable marker of growth hormone status
Muscle growth and maintenance
Bone density
Tissue repair and recovery
Cognitive function
Risks if abnormal:
Low: muscle wasting, poor recovery, fatigue, accelerated aging
High: acromegaly, possibly increased cancer risk (growth promotion)
Sweet spot: adequate for repair without excessive growth signaling
What Can Cause Abnormal Levels?
Aging (low)
55% likelyIGF-1 peaks in puberty and declines ~14% per decade after age 30 ("somatopause").
GH Deficiency (low)
30% likelyPituitary dysfunction reduces GH output, lowering IGF-1.
Malnutrition/Low Protein
Adequate protein and calories are required for IGF-1 production.
Liver Disease
The liver produces IGF-1. Cirrhosis impairs production.
Sleep Deprivation
GH is primarily released during deep sleep. Poor sleep = less GH = less IGF-1.
Chronic Illness/Inflammation
Inflammatory cytokines suppress IGF-1 production.
What You Can Do
Deep sleep optimization: 7-9 hours, consistent schedule
Impact: GH pulses primarily during deep (stage 3) sleep \u00B7 Timeline: 2-4 weeks
High-intensity exercise and resistance training
Impact: Both acutely spike GH release \u00B7 Timeline: 4-8 weeks
Adequate protein: 1.2-1.6g/kg body weight daily
Impact: Protein provides amino acids for IGF-1 production \u00B7 Timeline: 4-8 weeks
If lifestyle changes aren't enough:
Intermittent fasting (16:8 or similar)
Impact: Fasting increases GH release 2-5x. Paradoxically, this raises IGF-1 production capacity. \u00B7 Timeline: 4-8 weeks
Reduce sugar and refined carbs
Impact: Hyperinsulinemia impairs GH release \u00B7 Timeline: 4-8 weeks
Arginine: 5-9g before bed on empty stomach
Impact: Amino acid that stimulates GH release \u00B7 Timeline: 4-8 weeks
Recommended retest: 3-6 months
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