IGF-1, or Insulin-Like Growth Factor 1, is a hormone similar in structure to insulin, but its main function is to promote growth and cell development.
It is primarily produced in the liver in response to growth hormone (GH) stimulation from the pituitary gland. Because of this, IGF-1 is also known as somatomedin C.
🔁 How IGF-1 Fits Into the Hormonal System
The GH–IGF-1 Axis:
- The hypothalamus releases GHRH (Growth Hormone-Releasing Hormone).
- This stimulates the anterior pituitary to release GH (Growth Hormone).
- GH travels to the liver, where it triggers production of IGF-1.
- IGF-1 travels through the blood and acts on various tissues to:
- Stimulate bone and muscle growth
- Promote cell division and repair
- Support organ development
➕ IGF-1 also provides negative feedback:
- High levels of IGF-1 signal the pituitary and hypothalamus to reduce GH production.
🏗️ What Does IGF-1 Do?
| Function | Description |
|---|---|
| 📏 Stimulates Growth | Increases bone length and muscle mass (especially in children) |
| 🛠️ Promotes Repair | Enhances cell regeneration, DNA synthesis, and tissue repair |
| 💪 Builds Muscle | Increases protein synthesis in muscle cells |
| 🧃 Affects Metabolism | Regulates fat storage, insulin sensitivity, and blood sugar |
| 🧠 Supports Development | Plays a role in nerve development, brain growth, and myelination |
🧪 IGF-1 Testing
IGF-1 levels are commonly measured in blood to:
- Evaluate growth disorders (short stature in children, GH deficiency)
- Diagnose acromegaly or gigantism (excess GH)
- Monitor GH therapy
- Detect pituitary or hypothalamic disorders
Because GH is secreted in pulses, it can be hard to measure accurately — but IGF-1 stays stable in the blood, making it a reliable marker of GH activity.
📉 Low IGF-1 May Indicate:
- Growth hormone deficiency
- Liver disease
- Malnutrition or undernourishment
- Hypothyroidism
- Chronic illness or inflammation
In Children:
- Short stature
- Delayed puberty
- Poor bone growth
In Adults:
- Fatigue, muscle loss, poor recovery
- Increased body fat, especially around the waist
📈 High IGF-1 May Indicate:
- Excess GH, such as from:
- Pituitary tumor (acromegaly/gigantism)
- GH-secreting tumors elsewhere (rare)
- Puberty
- GH therapy (over-replacement)
🧠 IGF-1 and Aging
- IGF-1 levels peak during adolescence and decline with age.
- Low IGF-1 in older adults has been associated with frailty, but high levels may increase the risk of certain cancers.
- Balancing IGF-1 is a subject of longevity and anti-aging research, but increasing it unnaturally (e.g., with GH abuse) may carry serious risks.
🧠 Summary Table:
| Feature | IGF-1 (Insulin-Like Growth Factor 1) |
|---|---|
| Produced by | Liver (primarily), in response to GH |
| Stimulated by | Growth Hormone (GH) |
| Acts on | Bones, muscles, organs, and other body tissues |
| Functions | Promotes growth, cell repair, metabolism |
| Clinical uses | Diagnosing GH-related disorders, monitoring therapy |
| Feedback control | Inhibits GH via negative feedback to pituitary |