Insulin-like Growth Factor (IGF)
Insulin-like Growth Factors (IGFs) are peptide hormones structurally similar to insulin, playing a key role in growth, development, and cellular regulation. There are two main types:
IGF-1 (Insulin-like Growth Factor 1)
- Primarily produced in the liver in response to growth hormone (GH) stimulation.
- Acts as the main mediator of the anabolic and growth-promoting effects of GH.
- Essential for childhood growth and contributes to tissue repair, muscle maintenance, and metabolic regulation in adulthood.
- Levels decline with age and are influenced by nutrition, exercise, and health status.
IGF-2 (Insulin-like Growth Factor 2)
- More active during fetal development.
- Functions largely independent of GH.
- Its role in adults remains less clearly understood.
Biological Properties
- Mitogenic: Stimulates cell proliferation.
- Anti-apoptotic: Promotes cell survival.
- Binds to IGF receptors, especially IGF-1R, activating pathways such as PI3K-AKT and MAPK.
- Circulates bound to IGF-binding proteins (IGFBPs), especially IGFBP-3, which regulate its bioavailability.
Clinical Relevance
- ↑ IGF-1: Associated with acromegaly, neoplasms, and insulin resistance.
- ↓ IGF-1: Linked to growth disorders, frailty, osteoporosis, and aging.