Insulin-Like Growth Factor I (IGF-1)

Other names: IGF 1, LC/MS, INSULIN LIKE GROWTH FACTOR-1, Human IGF-I (ng/mL), Somatomedin C, IGF I, LC/MS

Optimal Result: 64 - 240 ng/dL, or 8.36 - 31.37 nmol/L.

Insulin-Like Growth Factor I (IGF-1)

What is IGF-1?

Insulin-Like Growth Factor I (IGF-1) is a hormone primarily produced by the liver in response to stimulation by Growth Hormone (GH). It plays a crucial role in promoting normal growth and development, especially during childhood and adolescence. IGF-1 continues to influence cellular repair, muscle maintenance, and tissue regeneration throughout adulthood, making it a key biomarker for evaluating growth hormone function, metabolic health, and aging-related conditions.

Although structurally similar to insulin, IGF-1 has distinct biological effects. It acts as a mediator of growth hormone activity, carrying out many of GH’s anabolic functions in tissues such as bone, muscle, cartilage, and skin.


How IGF-1 Works in the Body

Growth Hormone (GH), secreted by the anterior pituitary gland, stimulates the liver and other tissues to produce IGF-1. Once in circulation, IGF-1 binds to specific IGF-1 receptors on the surface of cells, activating pathways that promote:

  • Cellular growth and proliferation
    IGF-1 stimulates the replication of cells in bones, muscles, and organs, making it essential during periods of rapid growth, such as puberty.

  • Tissue repair and regeneration
    It enhances protein synthesis and supports the repair of damaged tissues, including muscle, bone, skin, and intestinal lining.

  • Bone density and skeletal development
    IGF-1 plays a critical role in bone remodeling by supporting both osteoblast (bone-building) and osteoclast (bone-resorbing) activity.

  • Muscle growth and metabolic balance
    IGF-1 increases muscle protein synthesis, reduces muscle breakdown, and may contribute to maintaining insulin sensitivity and glucose metabolism.


Why IGF-1 Testing Is Important

Measuring IGF-1 levels provides an indirect but reliable indicator of growth hormone activity, as IGF-1 levels remain relatively stable throughout the day compared to the pulsatile nature of GH. IGF-1 testing is commonly used in the evaluation of:

  • Growth disorders in children and adolescents

  • Suspected adult growth hormone deficiency

  • Acromegaly and gigantism (excess growth hormone conditions)

  • Anti-aging and regenerative medicine programs

  • Monitoring GH therapy

  • Nutritional and chronic disease status

Abnormally high or low IGF-1 levels can signal disruptions in the GH–IGF axis, often linked to endocrine disorders, liver dysfunction, malnutrition, or chronic inflammatory conditions.


IGF-1 Reference Ranges by Age

IGF-1 levels naturally decline with age. Therefore, interpretation is age-specific. Although reference ranges may vary slightly by laboratory, typical ranges are approximately:

  • Ages 16–24: 182 to 780 ng/mL

  • Ages 25–39: 114 to 492 ng/mL

  • Ages 40–54: 90 to 360 ng/mL

  • Ages 55+: 71 to 290 ng/mL

Low IGF-1 levels in adults may suggest growth hormone deficiency, chronic illness, undernutrition, or age-related decline. Elevated IGF-1 levels may be associated with acromegaly or excessive GH therapy.


Factors That Influence IGF-1 Levels

  • Age: IGF-1 peaks during puberty and gradually declines with aging.

  • Nutrition: Malnutrition, especially protein deficiency, lowers IGF-1.

  • Liver health: As the liver produces IGF-1, liver disease can suppress its levels.

  • Hormonal disorders: Pituitary dysfunction, GH resistance, or excess GH can alter IGF-1.

  • Medications: GH therapy increases IGF-1; corticosteroids and estrogen may reduce it.


Clinical and Research Relevance

Due to its central role in tissue growth and metabolic health, IGF-1 is increasingly studied in contexts such as:

  • Aging and longevity: Both high and low IGF-1 levels have been linked to different aspects of aging and disease risk.

  • Muscle wasting disorders: IGF-1 may help in evaluating sarcopenia and cachexia.

  • Metabolic health: Emerging research links IGF-1 levels with insulin sensitivity, diabetes risk, and cardiovascular disease.

  • Cancer: Elevated IGF-1 has been investigated for potential associations with increased cell proliferation and cancer risk, particularly in hormone-sensitive tissues.


Bottom Line

IGF-1 is a powerful growth-promoting hormone and a key marker of the body's anabolic (building and repair) capacity. Whether evaluating a child’s growth concerns, investigating adult hormone imbalance, or monitoring age-related changes, IGF-1 offers valuable insights into growth hormone activity and overall metabolic health. Testing IGF-1 levels can guide both diagnosis and treatment across a range of endocrine, metabolic, and regenerative conditions.

 

What does it mean if your Insulin-Like Growth Factor I (IGF-1) result is too high?

Elevated IGF-1 Levels: Causes, Symptoms, Diagnosis, and Treatment

Insulin-Like Growth Factor I (IGF-1) is a hormone primarily produced by the liver in response to growth hormone (GH). It plays a major role in growth, tissue repair, and metabolic regulation. When IGF-1 levels are too high, it often reflects excessive growth hormone activity, which can lead to serious health issues over time—especially if left untreated.

Elevated IGF-1 is most commonly associated with acromegaly in adults and gigantism in children and adolescents. These conditions are often caused by noncancerous tumors in the pituitary gland that stimulate overproduction of GH.


Quick Summary: Elevated IGF-1 at a Glance

  • Definition: IGF-1 is a hormone that mirrors growth hormone activity in the body.

  • Main Cause of Elevation: Excess GH production, often due to a pituitary tumor.

  • Associated Conditions: Acromegaly (adults) and gigantism (children).

  • Next Steps: Confirm with GH testing and imaging (e.g., MRI), and develop a treatment plan with your doctor.


What Causes High IGF-1 Levels?

High IGF-1 levels are typically due to growth hormone overproduction, which overstimulates the liver’s release of IGF-1. Common causes include:

  • Acromegaly (adults): A hormonal disorder that causes enlarged hands, feet, facial features, and internal organs over time.

  • Gigantism (children): Excess GH during developmental years causes abnormally rapid height and bone growth.

  • Pituitary adenomas: Noncancerous tumors of the pituitary gland are the most common cause of GH and IGF-1 overproduction.

  • GH therapy overdose: Rarely, IGF-1 may be elevated in people receiving excessive GH treatment.


Diagnosing Elevated IGF-1 Levels

Because GH levels fluctuate throughout the day, IGF-1 provides a more stable and reliable measure of average GH activity.

Testing and diagnosis typically involve:

  1. IGF-1 Blood Test

    • Elevated IGF-1 suggests chronic GH overproduction.

  2. GH Testing

    • A glucose suppression test may be used to check if GH remains high when it should be suppressed.

  3. Imaging

    • MRI of the pituitary gland is commonly ordered to look for a tumor causing hormone excess.

  4. Other lab tests

    • Blood sugar, insulin, thyroid, and liver function tests may help assess related complications.


Symptoms of Elevated IGF-1

Symptoms often develop gradually and may go unnoticed at first. They vary based on the severity and underlying cause:

In Adults (Acromegaly):

  • Enlarged hands, feet, and facial bones (jaw, nose, forehead)

  • Joint pain, arthritis, or carpal tunnel syndrome

  • Thickened skin and enlarged tongue

  • Deepened voice

  • Excessive sweating

  • Fatigue and muscle weakness

  • Headaches or vision changes (due to tumor pressure)

  • Irregular menstruation or erectile dysfunction

In Children (Gigantism):

  • Rapid and excessive growth in height

  • Delayed puberty

  • Muscle weakness

  • Enlarged facial features and hands/feet


Treatment Options for Elevated IGF-1

The main goal of treatment is to normalize IGF-1 and GH levels, reduce tumor size (if present), and prevent long-term complications.

1. Surgery

  • Transsphenoidal surgery to remove a pituitary tumor is often the first-line treatment for acromegaly or gigantism.

  • Can immediately reduce GH and IGF-1 levels in many patients.

2. Medications

  • Somatostatin analogs (e.g., octreotide, lanreotide): Reduce GH secretion.

  • GH receptor antagonists (e.g., pegvisomant): Block GH action at its target cells, lowering IGF-1.

  • Dopamine agonists (e.g., cabergoline): May help in some cases, especially with mild disease.

3. Radiation Therapy

  • Used when surgery and medications are not fully effective.

  • May take months or years to achieve full hormonal control.


Long-Term Monitoring and Follow-Up

Managing elevated IGF-1 is a lifelong process. Routine monitoring helps ensure that hormone levels remain controlled and complications are prevented:

  • Regular blood tests: To track IGF-1 and GH levels

  • Repeat MRI scans: To monitor tumor growth or recurrence

  • Monitoring for complications: Including diabetes, high blood pressure, joint damage, and sleep apnea

Early treatment significantly improves long-term health outcomes and quality of life.


Frequently Asked Questions (FAQ)

Can I have high IGF-1 without symptoms?
Yes. In early stages, many patients feel fine. Subtle symptoms can be overlooked, so lab testing is important.

Is high IGF-1 always caused by a tumor?
Most often, yes. Pituitary adenomas are the leading cause, but other rare conditions or excess GH therapy can also raise IGF-1.

Can high IGF-1 be dangerous?
Yes. Long-term elevation is linked to increased risks of heart disease, insulin resistance, sleep apnea, arthritis, and even certain cancers.

Does treatment normalize IGF-1?
In many cases, yes—especially with early diagnosis and effective surgery or medication. Ongoing monitoring is key.

Can lifestyle changes lower IGF-1?
Lifestyle changes alone are not sufficient when GH overproduction is the cause. However, managing blood sugar, weight, and sleep can support treatment.


Takeaway

  • Elevated IGF-1 is a marker of excess growth hormone activity, often due to pituitary tumors.

  • If untreated, high IGF-1 can cause serious complications including acromegaly, cardiovascular issues, diabetes, and joint disease.

  • Diagnosis and treatment are highly effective, especially when caught early.

  • Partner with your healthcare provider to confirm the cause, choose the right treatment, and monitor your long-term health.

 

What does it mean if your Insulin-Like Growth Factor I (IGF-1) result is too low?

Low IGF-1 Levels: Causes, Symptoms, and What You Should Do

Insulin-Like Growth Factor I (IGF-1) is a vital hormone primarily produced by the liver in response to growth hormone (GH). It plays an essential role in regulating growth, supporting tissue repair, maintaining muscle and bone health, and reflecting overall nutritional and metabolic status.

Low IGF-1 levels—especially when below the age-specific reference range—can point to growth hormone deficiency, GH resistance, malnutrition, or chronic illness. IGF-1 testing is often used alongside other hormone tests to diagnose pituitary disorders, growth abnormalities, or systemic metabolic conditions.


Quick Summary: Low IGF-1 at a Glance

  • What is IGF-1?
    A hormone regulated by growth hormone that supports growth, cellular repair, and tissue health.

  • Main Causes of Low IGF-1:
    GH deficiency, pituitary or hypothalamic dysfunction, malnutrition, chronic diseases, or aging.

  • Who Should Be Tested?
    Individuals with unexplained fatigue, muscle loss, poor growth in children, or suspected hormone imbalance.

  • Next Steps:
    Work with your healthcare provider to identify the root cause and explore appropriate treatment or lifestyle strategies.


What Does a Low IGF-1 Level Mean?

A low IGF-1 result (especially if below the age-adjusted reference range) may indicate:

  • Growth Hormone (GH) Deficiency
    The most common cause. IGF-1 levels are more stable than GH, making IGF-1 a more reliable marker of GH status.

  • GH Resistance or Insensitivity
    The body produces GH, but tissues do not respond to it—leading to persistently low IGF-1 levels despite normal or high GH levels.

  • Pituitary or Hypothalamic Dysfunction
    Tumors, trauma, surgery, or radiation can impair GH production, leading to secondary IGF-1 deficiency.

  • Malnutrition or Anorexia
    IGF-1 is highly sensitive to nutritional status and often decreases before other markers like prealbumin or transferrin.

  • Chronic Illness or Inflammatory States
    Conditions such as liver disease, kidney disease, or poorly controlled diabetes can suppress IGF-1 production.

  • Aging
    IGF-1 levels decline naturally with age, but significantly low levels—even in older adults—can reflect endocrine or systemic health concerns.


Low IGF-1: Causes and Clinical Significance

Cause Key Features Clinical Relevance
GH deficiency Low GH and low IGF-1 Suggests pituitary or hypothalamic dysfunction
GH resistance/insensitivity Normal or high GH, low IGF-1 May indicate genetic or acquired resistance
Pituitary damage History of trauma, tumor, surgery Points to central GH deficiency
Malnutrition/anorexia Low body weight and low IGF-1 Early and sensitive marker of inadequate nutrition
Chronic illness (e.g., CKD, liver disease) Low IGF-1 with systemic symptoms Supports diagnosis and disease monitoring
Aging Gradual decline over time Expected, but very low levels may need evaluation

How IGF-1 Testing Fits Into Diagnosis

IGF-1 is frequently tested alongside or in place of IGF Binding Protein 3 (IGFBP-3) to evaluate GH activity. In most cases, IGF-1 offers superior diagnostic accuracy, particularly when diagnosing growth hormone deficiency, acromegaly, or GH resistance.

Low IGF-1 strongly suggests:

  • Complete or partial growth hormone deficiency

  • GH resistance or insensitivity

  • Severe undernutrition or catabolic stress

A normal IGF-1 result does not rule out mild GH deficiency or early-stage resistance. Clinical context matters.


Recognizing Symptoms of Low IGF-1

You may not always feel symptoms, but when present, they can include:

  • Persistent fatigue or low energy

  • Muscle loss or reduced strength

  • Increased abdominal or visceral fat

  • Low bone density or osteoporosis

  • Slower healing or recovery

  • Stunted growth or delayed puberty (in children)

  • Mood changes, poor memory, or lower quality of life


IGF-1 in Growth Hormone Therapy

For individuals undergoing GH therapy (children with growth delays, adults with diagnosed GH deficiency), IGF-1 monitoring helps guide treatment:

  • Goal: Maintain IGF-1 within the normal reference range, ideally in the middle-to-upper third for your age.

  • If IGF-1 is too high: Higher levels do not improve outcomes and may increase side effects over time.

  • If IGF-1 remains low despite treatment: This may suggest GH underdosing, poor absorption, or resistance—your provider may adjust your plan accordingly.


When Is Additional Testing Needed?

If your IGF-1 is low, your doctor may recommend:

  • Growth Hormone Stimulation Testing to confirm GH deficiency

  • Pituitary MRI if a tumor or structural issue is suspected

  • Blood work to evaluate thyroid function, liver health, kidney function, or nutritional deficiencies

  • Follow-up testing after lifestyle, nutritional, or therapeutic interventions


Frequently Asked Questions (FAQ)

Is low IGF-1 always dangerous?
Not always. A gradual decline is part of normal aging. But if IGF-1 is very low—especially with symptoms or in younger individuals—it may signal an underlying condition.

Can IGF-1 be improved naturally?
Yes. Addressing malnutrition, managing chronic illness, and increasing physical activity may help. In medically indicated cases, GH therapy may also be used.

Do children and adults have different IGF-1 targets?
Yes. IGF-1 reference ranges are age-specific, and treatment decisions differ between pediatric and adult cases.

Does normal IGF-1 mean GH function is normal?
Not necessarily. Mild GH deficiency or resistance may not show up in IGF-1 levels. Clinical signs are just as important as lab values.

What if I feel fine but my IGF-1 is low?
If you're asymptomatic and otherwise healthy, your provider may monitor rather than treat. But very low levels always deserve a closer look.


Takeaway

  • Low IGF-1 can reflect growth hormone issues, malnutrition, or systemic illness—even when other lab values appear normal.

  • It’s not just a marker of growth—IGF-1 reflects your body's repair, metabolic balance, and hormonal health.

  • Partner with your provider to explore the cause, monitor changes, and build a tailored treatment or wellness plan.

 

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