Reflects Growth Hormone Activity, Tissue Repair Signaling & Metabolic Status

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 (GH) stimulation. It helps regulate cellular growth, repair, protein synthesis, and metabolic signaling. Because GH is secreted in pulses and varies throughout the day, IGF-1 is often used as a steadier indirect marker of overall GH activity.
IGF-1 plays a role in muscle and bone remodeling, recovery, glucose handling, and broader anabolic signaling. Levels are strongly influenced by age, nutrition (especially protein and total calories), insulin status, liver function, thyroid function, and inflammatory burden.

Why Test for IGF-1?

Evaluating IGF-1 helps clinicians assess GH signaling and anabolic status in a clinically practical way. IGF-1 testing is commonly used to investigate:

• Suspected growth hormone excess (e.g., acromegaly) or deficiency
•  Unexplained changes in lean mass, recovery capacity, or exercise tolerance
•  Low bone density or impaired tissue repair
•  Fatigue patterns that suggest neuroendocrine or pituitary involvement
•  Metabolic dysfunction, insulin resistance, or unfavorable body composition shifts
•  Monitoring response and safety in patients receiving GH therapy or related interventions
   inflammation, infection, or trauma.

IGF-1 is typically measured in serum and interpreted using age-adjusted reference intervals.

Clinical Significance of IGF-1 Levels

• Low IGF-1 Levels: Age-adjusted IGF-1 below the lab’s reference interval (often below ~80–120 ng/mL in many adults, depending on age and lab methodology) may reflect reduced GH output, impaired hepatic production, undernutrition/low protein intake, chronic inflammation, hypothyroidism, liver dysfunction, or pituitary-hypothalamic signaling issues. Clinically, low IGF-1 may be associated with reduced lean mass, poor recovery, low bone density, increased central fat gain, low exercise tolerance, or slower wound healing—though symptoms and age context matter.
• High IGF-1 Levels: Age-adjusted IGF-1 above the lab’s reference interval (often above ~250–350 ng/mL in many adults, depending on age and lab methodology) can be associated with GH excess (e.g., acromegaly), exogenous GH/peptide use, hyperinsulinemia/insulin resistance in some contexts, or increased anabolic/proliferative signaling. Persistently elevated IGF-1 may track with sleep disruption, edema, joint discomfort, headaches, carpal tunnel-like symptoms, or worsening glycemic control in susceptible patients. In long-term risk discussions, higher IGF-1 can raise concern for pro-proliferative signaling, especially when paired with other risk factors.

Actionable Insights

IGF-1 should be interpreted in context rather than as an isolated value. A single IGF-1 measurement reflects overall GH exposure but does not confirm rhythm, dosing patterns (if therapy is used), or downstream metabolic impact. An IGF-1 value within range does not guarantee healthy signaling—patients may still have poor recovery, adverse glycemic patterns, or symptoms suggesting imbalance. IGF-1 is commonly evaluated alongside glucose/insulin markers, thyroid function, liver function, and broader hormone testing to assess anabolic signaling, metabolic tolerance, and recovery capacity.
When abnormalities are identified, clinical focus often shifts to upstream drivers such as protein intake and energy availability, sleep quality, insulin resistance, thyroid status, hepatic function, inflammation, medication effects, and (when relevant) GH/peptide exposure. Monitoring trends over time may provide more insight than one-time measurements, especially when therapy or lifestyle changes are introduced.

Optimal Ranges

• IGF-1 (Serum): Age-adjusted reference intervals vary widely by lab; interpret using the lab’s age-banded range
•  General functional aim (clinical context dependent): mid-range for age, avoiding persistent low-end deficiency patterns or high-end elevations

Note: Reference ranges vary by laboratory. In functional medicine, some providers may consider a narrower interpretive window to help guide clinical context. These values are not standardized and should be interpreted in conjunction with the ordering provider’s judgment.

“A key cautionary takeaway is that persistently elevated IGF-1 levels in a patient not using GH, peptides, or other anabolic supplements warrant prompt consideration of underlying proliferative risks, including increased likelihood of breast and prostate cancer.”

Dr. Mitch Ghen

Disclaimer: Content on the Access Labs blog is for informational purposes only and reflects the views of individual contributors, not necessarily those of Access Labs. We do not endorse specific treatments, products, or protocols. This content is not a substitute for professional medical advice. Always consult a qualified healthcare provider regarding any medical concerns.