Insulin-like Growth Factor 1 (IGF-1) is a polypeptide hormone central to growth and metabolism. It acts as the primary mediator for many of Growth Hormone (GH) effects on tissues. While necessary for normal development, persistently high levels warrant medical attention. Sustained elevation can signal an underlying disorder and lead to significant health complications over time.
What is IGF-1 and Its Normal Role
Insulin-like Growth Factor 1 is a protein hormone predominantly synthesized in the liver in response to stimulation by Growth Hormone (GH), which is released from the pituitary gland. IGF-1 travels through the bloodstream to distant target tissues. Most IGF-1 circulating in the blood is bound to carrier proteins, which controls its half-life and bioavailability to cells.
This hormone is a powerful stimulator of cell growth, proliferation, and differentiation throughout the body. Its functions include promoting the growth of skeletal muscle and cartilage, increasing bone density, and maintaining tissue structure. IGF-1 also works alongside insulin to regulate glucose and lipid metabolism. Because GH is released in pulses throughout the day, measuring stable IGF-1 levels provides a reliable indicator of the body’s average GH activity.
Primary Causes of Chronically Elevated Levels
A sustained elevation of IGF-1 often points to an underlying pathological condition involving Growth Hormone (GH) overproduction. The most common cause in adults is acromegaly, a rare disease typically caused by a non-cancerous pituitary tumor (adenoma). This tumor secretes excessive GH, which drives up IGF-1 production in the liver.
If GH hypersecretion occurs before bone growth plates close, it results in gigantism, leading to abnormal height and body size. In adults, the excess hormone causes bones and soft tissues to thicken since bones cannot lengthen. IGF-1 levels can also be physiologically elevated during childhood, peaking during the pubertal growth spurt, and during pregnancy. Another cause of elevated IGF-1 is the misuse of exogenous GH or related substances, such as those used for performance enhancement.
Health Risks Associated with High IGF-1
The long-term effects of persistently high IGF-1 levels are systemic, influencing multiple organ systems. Continuous stimulation of cell proliferation leads to a general overgrowth of soft tissues and organs, known as visceromegaly. This includes the enlargement of the heart muscle (cardiomegaly), which contributes to heart failure and increased cardiovascular mortality.
Excess IGF-1 also promotes characteristic skeletal changes, such as the thickening of bones in the face, hands, and feet, and can cause joint pain and destructive arthritis. Metabolic disorders are common, as chronic hormone excess leads to insulin resistance, increasing the risk of developing Type 2 Diabetes. High IGF-1 levels are also associated with increased risk for certain cancers, including colorectal, prostate, breast, and thyroid cancer. This link is attributed to IGF-1’s role as a growth-promoting factor that stimulates the proliferation and survival of cancer cells.
Medical Monitoring and Treatment Approaches
The medical workup for suspected high IGF-1 levels begins with a blood test, followed by a diagnostic confirmation test such as the Oral Glucose Tolerance Test (OGTT). In healthy individuals, ingesting glucose suppresses Growth Hormone (GH) secretion; failure of this suppression confirms GH hypersecretion. The primary goal of treatment is to normalize both GH and IGF-1 levels to reduce symptoms and health risks.
Treatment strategies are multimodal and depend on the underlying cause, most commonly a pituitary adenoma. The first-line intervention is often surgical removal of the tumor, which can be curative for smaller growths. If surgery is unsuccessful or not feasible, pharmacological interventions are used. These include Somatostatin Analogues, which suppress GH release from the pituitary gland, and Growth Hormone Receptor Antagonists, which block GH action at the tissue level. Regular, long-term monitoring of IGF-1 levels is essential after treatment to ensure control and guide necessary adjustments to therapy.