Insulin-like Growth Factor 1 (IGF-1) is a protein that shares structural similarities with insulin. This hormone is involved in various biological processes from early development through adulthood, contributing to tissue maintenance and overall physiological balance.
How the Body Produces and Regulates IGF-1
The liver is the primary site for IGF-1 production, largely stimulated by growth hormone (GH). This interaction forms the GH-IGF-1 axis, a system coordinating growth and metabolic functions. When GH is released from the pituitary gland, it travels to the liver, prompting IGF-1 release into the bloodstream.
Nutritional factors also influence IGF-1 production; adequate protein intake and insulin levels help maintain proper concentrations. Approximately 98% of circulating IGF-1 is bound to specific binding proteins (IGF-BPs), primarily IGFBP-3. These proteins regulate IGF-1’s availability and activity in tissues, preventing excessive stimulation. IGF-1 levels peak during puberty to support rapid growth and gradually decline with age.
Essential Functions of IGF-1
IGF-1 promotes the growth and division of cells across nearly all body tissues, including skeletal muscle, cartilage, bone, and nerve cells. It contributes to overall body growth and the maintenance of various organ systems. The hormone also aids in tissue repair and regeneration by fostering cell proliferation and inhibiting programmed cell death.
IGF-1 significantly impacts metabolism by influencing how cells utilize glucose and synthesize proteins. It enhances glucose uptake in cells and promotes protein synthesis, relevant for muscle growth and strength development. The hormone also supports bone density by stimulating bone-forming cells and inhibiting bone breakdown. It contributes to the development and function of the nervous system, including neurogenesis and myelination.
IGF-1 and Its Role in Health and Disease
Variations in IGF-1 levels can have implications for health. Abnormally low levels during childhood can contribute to growth disorders like dwarfism. Conversely, excessively high levels may be associated with conditions such as gigantism.
In metabolic health, IGF-1 influences how cells respond to insulin. Low IGF-1 levels have been linked to an increased likelihood of metabolic syndrome, a cluster of conditions heightening the risk for type 2 diabetes and heart disease. The relationship between IGF-1 and aging is actively researched; some studies suggest lower levels in older age might be associated with extended longevity in certain animal models, while others indicate a mid-range level is associated with the lowest mortality risk in humans.
The role of IGF-1 in cancer is complex and continues to be investigated. Elevated levels have been associated with an increased risk for certain cancers, including prostate, breast, and lung, potentially by promoting cell growth and inhibiting cell death in existing cancerous cells. However, both very low and very high IGF-1 levels may increase overall mortality risk, highlighting the importance of maintaining levels within a healthy range.