IGF-1

Introduction

Insulin-like Growth Factor-​1 (IGF-1), also known as somatomedin C, plays a pivotal role in the body’s growth and development. As a Nurse Practitioner with an autonomous practice in Florida, I regularly encounter patients with concerns regarding growth, metabolism, and overall health. Understanding biomarkers like IGF-1 can be a valuable tool in assessing and managing various health conditions. This article aims to provide an in-depth exploration of IGF-1, its background, clinical implications, and factors influencing its levels.

Background of IGF-1

IGF-1 is a hormone structurally similar to insulin, primarily produced in the liver as a response to growth hormone stimulation from the pituitary gland. It is instrumental in promoting the normal development of bones, tissues, and lean muscle mass. The production and regulation of IGF-1 are closely linked with nutrient intake and insulin resistance.

IGF-1 and Growth Hormone

Growth hormone, secreted by the pituitary gland, is a significant driver for IGF-1 production. Once stimulated, IGF-1 mediates many actions of the growth hormone, including bone growth and tissue development. This hormone’s levels are remarkably stable throughout the day, making it a reliable indicator for evaluating growth hormone activity, which tends to fluctuate.

Ranges and Standard Measurements

The levels of IGF-1 vary considerably with age, and understanding these ranges is crucial for accurate clinical assessment. The standard ranges, as provided by QUEST Diagnostics, are as follows:

• 18–19.9 Years: 108–548 ng/mL
  
• 20–24.9 Years: 83–456 ng/mL
  
• 25–29.9 Years: 63–373 ng/mL
  
• 30–39.9 Years: 53–331 ng/mL
  
• 40–49.9 Years: 52–328 ng/mL
  
• 50–59.9 Years: 50–317 ng/mL
  
• 60–69.9 Years: 41–279 ng/mL
  
• 70–79.9 Years: 34–245 ng/mL
  
• 80 Years: 34–246 ng/mL
  
  
  

The optimal range for individuals in their 30s is typically between 92.00–300.00 ng/mL, but it’s essential to consider age-related variability when interpreting results.

Clinical Implications of IGF-1 Levels

Low IGF-1 Levels

A decrease in IGF-1 can have several clinical implications:

• Metabolic Syndrome: Low IGF-1 is associated with metabolic disturbances, including an impaired lipid profile, insulin resistance, elevated glucose, cardiovascular disease, and obesity. Obese patients with low normal IGF-1 tend to have worse cardiovascular outcomes.
  
• Bone Density Decrease: Reduced IGF-1 levels can lead to decreased bone density, increasing the risk of fractures.
  
• Lean Body Mass Decrease: Insufficient IGF-1 may contribute to a reduction in lean body mass and muscle strength.
  
• Lipid Level Abnormalities: IGF-1 plays a critical role in lipid and carbohydrate metabolism. Its insufficiency may lead to increased blood lipid levels.
  
• Fatigue and Reduced Exercise Tolerance: Adults with abnormally low IGF-1 may experience fatigue and reduced exercise tolerance.
  
• Neurological Concerns: Low IGF-1 levels have been linked to the development of dementia, including Alzheimer’s disease, with higher levels correlating with greater brain volume in non-demented individuals.
  
• Growth Hormone Resistance: Conditions like chronic disease, malnutrition, hypothyroidism, sex hormone deficiency, and genetic factors can contribute to growth hormone resistance, affecting IGF-1 production.
  
• Liver Disease: Patients with cirrhosis or liver dysfunction often have significantly reduced IGF-1 levels.
  
• Pituitary Gland Dysfunction: Damage or dysfunction in the pituitary gland can reduce growth hormone production, subsequently lowering IGF-1 levels.
  
• Short Stature in Children: Insufficient IGF-1 during childhood can inhibit bone growth and overall development.
  
  

High IGF-1 Levels

Conversely, elevated IGF-1 levels can lead to:

• Abnormal Growth: Excess IGF-1 and growth hormone can cause conditions like gigantism or acromegaly, characterized by abnormal skeleton growth, enlarged organs, and increased risk of cardiovascular diseases.
  
• Cancer Risk Increase: IGF-1 may promote the growth of prostate, breast, lung, and colon cancer by stimulating cell growth and inhibiting cell death.
  
• Insulin Resistance and Obesity: High IGF-1 levels are linked to increased circulating insulin levels due to obesity and excessive intake of simple sugars.
  
• Pituitary Gland Tumor: A pituitary tumor, often benign, is the primary cause of elevated growth hormone, leading to increased IGF-1 production. A glucose suppression test can help confirm the presence of a growth hormone–producing pituitary tumor.
  
  

Interfering Factors and Drug Associations

Several factors can interfere with IGF-1 levels:

• Nutrient Intake: Reduced caloric, protein, or carbohydrate intake can decrease IGF-1 levels.
  
• Insulin Levels: Elevated insulin levels can stimulate IGF-1 production.
  
• Chronic Illnesses: Conditions like liver dysfunction, hypothyroidism, and malnutrition can affect IGF-1 production.
  
• Medications: Certain drugs may influence IGF-1 levels, although specific drug associations need individualized assessment with a healthcare provider. Sermorelin is a synthetic growth hormone–releasing hormone (GHRH) analogue that stimulates the pituitary gland to increase natural growth hormone production.
  
  

Conclusion

In conclusion, a comprehensive evaluation by a functional medicine in Florida facilitates identification of cellular-level and molecular imbalances driving metabolic and developmental dysfunction. By integrating evidence-based therapies with longevity medicine medical care services—where hormonal regulation is often key—we offer patients a regenerative, preventive framework to rebuild resilience and optimize wellness. Call (904) 799-2531 or schedule online to request your personalized endocrine and metabolic health assessment.

Further Reading

• Le Roith D, Bondy C, Yakar S, Liu JL, Butler A. The somatomedin hypothesis: 2001. Endocrine Reviews. 2001;22(1):53–70. https://pubmed.ncbi.nlm.nih.gov/11157997/
  
• Jones JI, Clemmons DR. Insulin-like growth factors and their binding proteins: biological actions. Endocrine Reviews. 1995;16(1):3–34. https://pubmed.ncbi.nlm.nih.gov/7539020/
• Yakar S, Liu JL, Stannard B, Butler A, Accili D, Sauer B, LeRoith D. Normal growth and development in the absence of hepatic insulin-like growth factor I. Proc Natl Acad Sci U S A. 1999;96(13):7324–7329. https://pubmed.ncbi.nlm.nih.gov/10339643/