IGF-1 Blood Test: What High and Low Levels Can Tell You

If you’re chasing better recovery, unexplained fatigue, or changes in muscle and bone that don’t quite add up, IGF-1 is often a more useful place to look than growth hormone itself.

It’s also one of the more revealing biomarkers when something in your endocrine system – thyroid, liver, pituitary – isn’t functioning quite as it should.

Produced mainly by the liver in response to growth hormone, IGF-1 supports childhood growth and continues to influence bone health, muscle tissue, metabolism and cellular repair throughout adulthood.

It can also provide clinicians with a more practical indication of average growth hormone activity than a random growth hormone measurement.

That does not mean IGF-1 is a routine test that everyone needs.

High and low IGF-1 results can have several possible explanations. Levels may be influenced by age, nutrition, liver health, thyroid function, chronic illness and the use of exogenous human growth hormone, or HGH.

An IGF-1 result therefore needs to be interpreted in context. It cannot diagnose a growth hormone disorder or determine whether HGH use is safe on its own.

Here is what an IGF-1 blood test measures, why it may be requested and what could be behind an abnormal result.

 

Quick Facts

 

• IGF-1 stands for insulin-like growth factor 1.
• It is produced mainly by the liver following stimulation from growth hormone.
• IGF-1 is more stable throughout the day than growth hormone.
• An IGF-1 blood test may help investigate growth hormone excess or deficiency.
• Levels naturally change according to age and physiological circumstances.
• Exogenous HGH usually increases IGF-1 production.
• A high or low result is not a diagnosis on its own.
• Further dynamic hormone testing may be required when a growth hormone disorder is suspected.

 

What is Insulin-Like Growth Factor (IGF-1)?

 

Insulin-like growth factor 1 is a peptide hormone involved in growth, tissue development and metabolism.

Growth hormone is produced by the pituitary gland, a small gland situated at the base of the brain. Once released into the bloodstream, growth hormone signals the liver and other tissues to produce IGF-1.

IGF-1 then binds to receptors found throughout the body and contributes to processes including:

• Childhood growth and skeletal development
• Bone formation and maintenance
• Muscle tissue growth and repair
• Protein synthesis
• Cell growth and survival
• The metabolism of carbohydrates and fats
• The growth and maintenance of organs and other tissues

This communication pathway is commonly known as the growth hormone-IGF-1 axis.

It is sometimes simplified as “growth hormone sends the signal and IGF-1 carries it out”. This is useful as a starting point, although the real physiology is more complex.

Growth hormone also has direct effects on the body, while IGF-1 can be produced locally within tissues as well as by the liver.

IGF-1 also participates in a feedback system. As circulating IGF-1 rises, it helps signal the hypothalamus and pituitary gland to reduce further natural growth hormone secretion.

 

 

Is IGF-1 the same as growth hormone?

 

No. IGF-1 and growth hormone are closely connected, but they are different hormones.

Growth hormone is released by the pituitary gland in pulses. IGF-1 is produced mainly by the liver in response to growth hormone stimulation.

Growth hormone concentrations can change considerably within a short period. Secretion is influenced by factors including:

• Sleep
• Exercise
• Food intake
• Stress
• Age
• Blood glucose
• Other hormones

A random growth hormone result may therefore be low simply because the blood sample was collected between secretory pulses.

IGF-1 remains comparatively stable across the day.

This makes it more suitable as an initial blood marker when a clinician is assessing average growth hormone activity. NHS laboratory guidance describes IGF-1 as an index of growth hormone secretion used when investigating growth hormone deficiency or excess and when monitoring treatment.

However, IGF-1 is not a perfect substitute for growth hormone testing. Nutrition, liver health, thyroid function, age and chronic illness can affect the result independently of pituitary growth hormone production.

 

 

What is an IGF-1 blood test used for?

 

An IGF-1 blood test is most commonly used to investigate or monitor conditions involving excessive or insufficient growth hormone activity.

 

A clinician may request it when investigating:

 

• Possible growth hormone deficiency
• Known or suspected pituitary disease
• Prescribed growth hormone replacement
• Unexpectedly high IGF-1 during exogenous HGH use
• Symptoms developing after pituitary surgery or radiotherapy
• Multiple pituitary hormone deficiencies
• Suspected acromegaly in adults
• Suspected gigantism or unusual growth in children
• The response to treatment for a diagnosed growth hormone disorder

It may also be measured alongside other pituitary hormones when there are broader concerns about pituitary function.

An IGF-1 test is not usually intended as a general screening test for tiredness, poor gym recovery or changes in body composition.

These concerns are much more commonly related to factors such as sleep, nutrition, iron status, thyroid function, medication, stress or other health conditions.

 

 

Why test IGF-1 instead of growth hormone?

 

Growth hormone is released in short pulses, with some of the largest pulses occurring during deep sleep.

Between pulses, the amount present in the bloodstream may fall considerably. A single random growth hormone measurement may therefore provide a misleading picture of overall growth hormone production.

IGF-1 reflects the downstream effect of growth hormone exposure over a longer period and varies less across the day.

This makes it a more practical initial marker of the growth hormone-IGF-1 axis.

Even so, an IGF-1 result cannot always confirm or exclude a disorder.

When growth hormone deficiency is suspected in an adult, specialist growth hormone stimulation testing is often required. The Endocrine Society recommends stimulation testing for diagnosing suspected growth hormone deficiency rather than relying on a single IGF-1 or growth hormone measurement.

When growth hormone excess is suspected, a suppression test may be used to determine whether growth hormone falls appropriately after glucose is consumed.

 

 

What is a normal IGF-1 level?

 

There is no single IGF-1 concentration that is considered normal for every person.

IGF-1 levels change significantly throughout life. They are generally:

• Lower during early childhood
• Higher during puberty and adolescence
• Gradually lower throughout adulthood
• Influenced by sex and physiological circumstances

Laboratories therefore use age-adjusted and, where appropriate, sex-adjusted reference ranges.

A result that would be considered low for a younger adult may be entirely appropriate for an older adult. Results from different laboratories may also vary because of differences between testing platforms, assays and reference populations.

For this reason, IGF-1 should be interpreted using the range provided by the laboratory that analysed the sample.

Comparing your numerical result directly with someone else’s result, or with a range found online, may be misleading.

Some clinicians also consider an IGF-1 standard deviation score, sometimes called a Z-score. This indicates how far the result sits above or below the expected average for a person of the same age and sex.

 

 

What can cause High IGF-1 levels?

 

A significantly elevated IGF-1 result can indicate excessive growth hormone activity.

In adults, persistent natural growth hormone excess causes a rare condition called acromegaly.

Acromegaly is most commonly associated with a non-cancerous pituitary tumour that produces too much growth hormone.

The increased growth hormone stimulates excessive IGF-1 production and can gradually affect bones, soft tissues, metabolism and internal organs.

 

Possible signs and symptoms include:

 

• Hands or feet becoming larger
• Rings, shoes or gloves no longer fitting
• Gradual changes to facial features or the jaw
• Headaches
• Excessive sweating
• Oily or thickened skin
• Joint pain
• Tingling or numbness in the hands
• Fatigue
• Snoring or sleep apnoea
• Menstrual changes
• Erectile dysfunction
• High blood pressure
• Changes in blood glucose regulation

These changes can develop slowly and may not be immediately obvious. The NHS lists enlarged or swollen hands and feet, sweating, headaches, joint pain, sleep apnoea, thicker skin and changes in facial or body tissues among the possible symptoms of acromegaly.

Not every high IGF-1 result means that someone has acromegaly.

 

Other potential explanations include:

 

• Exogenous HGH or somatropin use
• Prescribed growth hormone replacement
• Puberty
• Pregnancy
• An age-inappropriate reference range
• Analytical or biological variation

A mildly elevated result may need to be repeated and assessed in context before further conclusions are drawn.

When natural growth hormone excess is suspected, further testing may include an oral glucose tolerance test to determine whether growth hormone suppresses normally.

Pituitary imaging may then be considered if the biochemical findings support the diagnosis.

 

How does exogenous HGH affect IGF-1?

 

Exogenous human growth hormone is growth hormone introduced into the body from an external source.

The manufactured form used medically is generally called somatropin. Depending on the preparation and indication, it may be administered as a daily or longer-acting injection.

Once administered, exogenous HGH stimulates the liver and other tissues to produce more IGF-1.

This means that a person using HGH will commonly experience an increase in IGF-1, although the extent of the rise can vary.

 

Factors influencing the response may include:

 

• The dose being used
• Frequency of administration
• Whether the preparation is daily or long-acting
• Treatment duration
• Age
• Sex
• Nutritional status
• Liver function
• Oestrogen use
• Individual sensitivity to growth hormone

IGF-1 is therefore commonly monitored during prescribed growth hormone treatment.

It provides a more stable indication of the biological response to growth hormone than a random serum growth hormone measurement.

Clinical guidance describes IGF-1 concentrations as one of the measures used when titrating prescribed growth hormone therapy, alongside treatment effects, symptoms and safety markers.

 

 

Prescribed HGH replacement versus non-prescribed use

 

There is an important difference between medically prescribed growth hormone replacement and the use of HGH for performance, physique or anti-ageing purposes.

Prescribed growth hormone may be offered to people with a confirmed clinical indication, such as proven growth hormone deficiency.

In these circumstances, treatment is normally supervised by a specialist. The dose may be adjusted according to:

• The underlying diagnosis
• Age
• Symptoms
• Side effects
• IGF-1 results
• Other pituitary hormones
• Glucose control
• Treatment response

 

The aim is not to increase IGF-1 as high as possible. It is to use an appropriate dose that treats the diagnosed condition while reducing the risk of excessive exposure.

Non-prescribed HGH use may take place without a confirmed deficiency, reliable dosing information or appropriate monitoring.

An IGF-1 test may show that growth hormone exposure is high, but it cannot confirm the quality or exact contents of an unregulated product. It also cannot make non-prescribed HGH use safe.

 

 

Can HGH cause a high IGF-1 result?

 

Yes.

Exogenous HGH is an important potential explanation for an elevated IGF-1 result.

Anyone interpreting the result should know:

• Whether HGH is being used
• Whether it has been prescribed
• The reported dose
• How frequently it is administered
• When the most recent dose was taken
• How long it has been used
• Whether it is a daily or long-acting preparation
• Whether other hormones or performance-enhancing drugs are being used

Without this information, an elevated result could be incorrectly interpreted as evidence of natural growth hormone excess.

However, reported HGH use should not automatically be assumed to explain every abnormal result.

A persistently high or unexpectedly elevated IGF-1 result should still be assessed clinically, particularly where there are symptoms associated with excessive growth hormone exposure.

 

 

What are the potential effects of excessive HGH exposure?

 

Using more growth hormone than the body requires may cause effects similar to natural growth hormone excess.

Possible adverse effects include:

• Fluid retention
• Swelling of the hands or feet
• Increased body weight due to fluid retention
• Joint or muscle pain
• Tingling or numbness
• Carpal tunnel symptoms
• Headaches
• Increased sweating
• Reduced insulin sensitivity
• Higher blood glucose
• Worsening diabetes
• Sleep apnoea symptoms
• Soft-tissue changes with prolonged excessive exposure

The likelihood and severity of these effects can depend on the dose, duration of exposure and the individual’s underlying health.

Somatropin medicine information lists headaches, muscle or joint pain and injection-site reactions among possible side effects.

Medical monitoring may also be needed for changes in glucose regulation and other complications.

 

 

Can IGF-1 tell you whether an HGH dose is safe?

 

Not by itself.

IGF-1 can provide useful information about the body’s response to growth hormone, but it should not be used as a standalone instruction for changing an HGH dose.

A result within the laboratory reference range does not prove that HGH use is safe or medically appropriate.

Similarly, a high result cannot be interpreted properly without knowing:

• The person’s age
• The reason HGH is being used
• The product and dosing schedule
• Treatment duration
• Symptoms and side effects
• Medical history
• Other blood test results

People receiving medically prescribed HGH should have the dose and monitoring managed by the responsible clinician.

A person should not increase, reduce or stop prescribed growth hormone solely because of one IGF-1 result without discussing it with their prescriber.

Where HGH is being used without medical supervision, an IGF-1 test may help identify excessive exposure, but it does not remove the wider risks associated with unsupervised treatment.

 

 

Can exogenous HGH suppress natural growth hormone production?

 

Exogenous HGH can influence the body’s normal feedback system.

As HGH increases IGF-1, the higher IGF-1 concentration can signal the hypothalamus and pituitary gland to reduce endogenous growth hormone secretion.

This means that a random growth hormone result collected while someone is using exogenous HGH may not reflect their natural growth hormone production.

Testing someone for suspected natural growth hormone deficiency while they are actively using HGH is therefore more complicated and requires specialist guidance.

Stopping prescribed growth hormone purely for testing purposes should only be done under the direction of the treating clinician.

 

 

Can someone have a normal IGF-1 result while using HGH?

 

 

Yes.

A person using exogenous HGH may still have an IGF-1 result within the laboratory reference range.

Possible explanations include:

• A relatively low dose
• Intermittent use
• Timing of the test
• Individual variation in response
• Poor absorption
• Differences between products
• Reduced liver responsiveness
• Undernutrition
• Oestrogen-related effects
• Laboratory and assay variation

A normal IGF-1 result does not confirm that HGH use is risk-free.

It also cannot confirm that a non-prescribed product contains the stated substance or dose.

Clinical assessment should consider symptoms, blood pressure, glucose regulation, thyroid function and the wider hormone picture rather than focusing exclusively on IGF-1.

 

 

What can cause Low IGF-1 levels?

 

A low IGF-1 result can occur when growth hormone production is reduced, but there are several other possible explanations.

 

Growth Hormone deficiency

 

The pituitary gland may not produce enough growth hormone because of:

• Pituitary or hypothalamic disease
• Previous pituitary surgery
• Radiotherapy
• Significant head trauma
• Structural abnormalities
• Other recognised causes of pituitary dysfunction

 

Adult growth hormone deficiency may be associated with reduced bone density, lower lean body mass, increased fat mass, reduced exercise capacity and impaired quality of life.

However, these features are non-specific and overlap with many other conditions.

A low IGF-1 result alone is not normally sufficient to diagnose adult growth hormone deficiency. Specialist assessment and a growth hormone stimulation test are often required.

 

Insufficient calorie or protein intake

 

IGF-1 production is sensitive to nutritional availability.

Low calorie intake, inadequate protein, malnutrition, eating disorders or prolonged fasting may reduce IGF-1, even when growth hormone secretion is normal or increased.

This is one reason why a low result cannot automatically be assumed to represent pituitary dysfunction.

 

Liver Disease

 

Most circulating IGF-1 is produced by the liver.

Significant liver dysfunction can therefore reduce IGF-1 production. Liver markers and the wider clinical history may need to be considered when interpreting a low result.

 

Hypothyroidism

 

Thyroid hormones interact with the growth hormone–IGF-1 axis.

Reduced thyroid hormone activity can affect growth hormone secretion and the liver’s response to growth hormone. Thyroid function may therefore be assessed when IGF-1 is unexpectedly low.

 

Chronic Kidney Disease

 

Kidney disease can disrupt the growth hormone–IGF-1 system and alter the activity of IGF-binding proteins.

The relationship is complex, so the result needs clinical interpretation rather than being viewed as an isolated number.

 

Chronic inflammation or illness

 

Long-term inflammatory disease, severe illness and other systemic conditions may suppress IGF-1 production or reduce the body’s responsiveness to growth hormone.

 

Glucocorticoid exposure

 

Long-term or high-dose corticosteroid use may interfere with growth hormone signalling and reduce the actions of IGF-1.

Medication history should always form part of the interpretation.

 

Poorly controlled diabetes

 

Metabolic health can influence the growth hormone–IGF-1 axis.

Poorly controlled diabetes, particularly where insulin availability is reduced, may lower circulating IGF-1 despite altered growth hormone secretion.

 

 

Does a low IGF-1 result explain fatigue or slow recovery?

 

 

Not necessarily.

Fatigue, reduced strength and slower recovery may occur in growth hormone deficiency, but they are extremely common in people who do not have a pituitary disorder.

Other possible contributors include:

• Iron deficiency or anaemia
• Thyroid dysfunction
• Insufficient sleep
• Low calorie or protein intake
• Excessive training load
• Vitamin deficiencies
• Chronic infection or inflammation
• Medication side effects
• Menopause or other hormonal changes
• Depression, anxiety or prolonged stress

Testing IGF-1 without considering these more common explanations may produce a result that is difficult to interpret and does not answer the original question.

The reason for testing should therefore be based on the wider clinical picture rather than one non-specific symptom.

 

IGF-1, Muscle and Exercise

 

IGF-1 contributes to normal muscle protein metabolism and tissue repair.

However, circulating IGF-1 is not a simple score of how well someone is building muscle or recovering from exercise.

Muscle adaptation is influenced by many factors, including:

• Training Stimulus
• Protein and total calorie intake
• Sleep
• Age
• Sex Hormones
• Thyroid Function
• Injury and inflammation
• Recovery time
• Genetics

 

Exercise can affect growth hormone secretion and local IGF-1 activity within muscle tissue, but a higher circulating IGF-1 result does not automatically mean better performance.

Similarly, an IGF-1 result near the lower end of the laboratory range does not prove that IGF-1 is responsible for slow recovery or difficulty gaining muscle.

 

IGF-1 and bone health

 

The growth hormone–IGF-1 axis supports bone growth during childhood and contributes to bone remodelling in adults.

Severe growth hormone deficiency can be associated with reduced bone mineral density.

However, bone health also depends on:

• Vitamin D status
• Calcium intake
• Sex hormones
• Body weight
• Resistance and weight-bearing exercise
• Smoking
• Alcohol intake
• Medication use
  Other medical conditions

IGF-1 may form part of an endocrine assessment, but it does not replace a complete evaluation of bone health.

 

IGF-1 and Ageing

 

Growth hormone secretion and IGF-1 levels tend to decline with age. This age-related change is sometimes referred to as the somatopause.

The term can be misleading when it is used to suggest that a normal age-related decline is automatically a hormone deficiency or requires treatment.

Ageing may also be accompanied by changes in muscle mass, bone density and body composition, but these changes cannot be attributed to IGF-1 alone.

An IGF-1 result should therefore be compared with an appropriate age-specific reference range.

Having a lower IGF-1 result than a much younger person is not, by itself, evidence of a medical problem.

Growth hormone treatment is not a routine anti-ageing treatment. It should be prescribed only when there is a recognised clinical indication and appropriate evidence supporting its use.

 

 

Can sleep affect IGF-1?

 

Sleep is connected to the growth hormone–IGF-1 axis because some of the largest natural growth hormone pulses occur during deep sleep.

Poor sleep may influence normal hormone secretion, but an isolated period of disrupted sleep does not necessarily cause a clinically significant IGF-1 abnormality.

Persistent sleep problems remain important to address, particularly when accompanied by:

• Loud snoring
• Witnessed breathing pauses
• Waking with headaches
• Daytime sleepiness
• Reduced concentration

Sleep apnoea can affect wider metabolic health and may also occur in people with excessive growth hormone exposure.

 

 

Do you need to fast for an IGF-1 blood test?

 

Fasting requirements can vary between laboratories and may depend on the other markers being measured at the same time.

IGF-1 itself is comparatively stable throughout the day, so strict timing is generally less important than it is for a random growth hormone measurement.

You should still follow the preparation instructions supplied with your test.

Tell the clinician or testing provider about:

• Prescribed growth hormone
• Non-prescribed HGH use
• The timing of your latest injection
• Whether you use a daily or long-acting preparation
• Corticosteroid medication
• Oestrogen-containing medication
• Diabetes medication
• Pregnancy
• Known liver or kidney disease
• Pituitary conditions
• Recent serious illness

Do not stop prescribed medication solely to prepare for a blood test unless the prescribing clinician has advised you to do so.

 

What other tests may be considered alongside IGF-1?

 

The most appropriate accompanying tests depend on why IGF-1 is being measured.

They may include:

• Growth hormone
• A growth hormone suppression test
• A growth hormone stimulation test
• Thyroid-Stimulating Hormone
• Free Thyroxine (FT4)
• Prolactin
• Cortisol and ACTH
• Luteinising Hormone (LH) and Follicle Stimulating Hormone (FSH)
• Oestradiol or testosterone
• Liver function tests
• Kidney function tests
• Fasting glucose
• HbA1c
• Full blood count
• Nutritional markers
• Pituitary MRI, where clinically indicated
• Where HGH is being used, monitoring may also consider blood pressure, fluid retention, glucose control and symptoms associated with excessive exposure.

Testing several unrelated hormones without a clear clinical question does not always provide a more useful answer.

The panel should be selected according to symptoms, medical history, medication and any known pituitary or endocrine condition.

 

When should an abnormal IGF-1 result be reviewed?

 

Speak with a qualified healthcare professional if your IGF-1 result is outside the laboratory reference range, particularly when:

• The result is significantly high or low
• The abnormality remains present on repeat testing
• You have a known pituitary condition
• You have had pituitary surgery or radiotherapy
• You have experienced significant head trauma
• Several pituitary hormone results are abnormal
• You are receiving prescribed growth hormone
• You are using non-prescribed HGH
• You have progressive changes in your hands, feet or facial features
• You have persistent headaches
• You have changes in vision
• A child has an unusual growth pattern
• Sudden severe headache, vomiting, visual disturbance, reduced consciousness or symptoms of acute pituitary dysfunction require urgent medical assessment.

 

 

Should you test your IGF-1?

 

IGF-1 testing can be valuable when there is a genuine reason to investigate the growth hormone–IGF-1 axis.

It may be appropriate for people with:

• Known pituitary disease
• Suspected growth hormone excess
• Possible growth hormone deficiency
• Prescribed growth hormone treatment
• Unexpected symptoms or results during HGH use
• Other clinical features suggesting pituitary dysfunction

 

It is less likely to be the first or most informative test for general tiredness, reduced fitness, poor recovery or difficulty changing body composition without additional features suggesting a growth hormone or pituitary disorder.

At My Atlas, we believe that blood testing should begin with a clear question.

Rather than measuring isolated biomarkers without context, the aim is to choose markers that are relevant to your symptoms and interpret them as part of a wider picture.

Where an IGF-1 result raises concern about growth hormone excess, growth hormone deficiency or inappropriate HGH exposure, suitable medical or endocrinology follow-up is essential.

 

Final Thoughts

 

IGF-1 is an important part of the body’s growth hormone system, but its role extends far beyond childhood growth.

It contributes to the maintenance of muscle, bone and other tissues while providing clinicians with a relatively stable marker of growth hormone activity.

It can also help monitor the body’s response to prescribed exogenous growth hormone.

The key word is context.

A high IGF-1 result does not automatically confirm acromegaly, and a low result does not automatically confirm growth hormone deficiency.

Similarly, an IGF-1 result within the reference range does not prove that non-prescribed HGH use is safe.

Age, nutrition, liver health, thyroid function, medication, chronic illness and exogenous HGH use can all influence the result.

IGF-1 is therefore most useful when it is tested for the right reason, interpreted against an appropriate reference range and assessed alongside the rest of your health information.

 

 

Frequently Asked Questions

 

What does IGF-1 stand for?

IGF-1 stands for insulin-like growth factor 1. It is a hormone produced mainly by the liver in response to growth hormone.

 

Is IGF-1 the same as growth hormone?

No. Growth hormone is produced by the pituitary gland. IGF-1 is produced mainly in response to growth hormone and carries out many of its growth-promoting effects.

 

Is IGF-1 more accurate than a growth hormone blood test?

IGF-1 is more stable throughout the day and is usually more informative than a single random growth hormone measurement. However, it cannot diagnose every growth hormone disorder by itself.

 

What causes high IGF-1?

Possible causes include natural growth hormone excess, prescribed or non-prescribed HGH use, pregnancy, puberty and differences in laboratory reference ranges. Persistent elevation may require further endocrine investigation.

Does taking HGH increase IGF-1?

Usually, yes. Exogenous HGH stimulates the liver and other tissues to produce more IGF-1.

The size of the increase depends on the dose, treatment schedule, age, liver function and individual response.

Can IGF-1 be used to monitor HGH use?

IGF-1 can help assess the body’s response to prescribed growth hormone. It should be interpreted alongside the dose, treatment schedule, symptoms, side effects and other health markers.

It should not be used alone to decide whether HGH use is safe.

 

Can HGH suppress natural growth hormone production?

Exogenous HGH and the resulting rise in IGF-1 can reduce natural pituitary growth hormone secretion through the body’s feedback system.

This can make assessment of natural growth hormone production more complicated while HGH is being used.

 

Can you use HGH and still have a normal IGF-1 result?

Yes. The response to HGH varies, and a person may remain within the laboratory reference range depending on dose, timing, treatment duration, product, liver responsiveness and other factors.

A normal IGF-1 result does not prove that HGH use is safe.

 

What causes low IGF-1?

Possible causes include growth hormone deficiency, insufficient calorie or protein intake, liver disease, hypothyroidism, chronic illness and certain medications.

 

Does low IGF-1 mean growth hormone deficiency?

Not necessarily. A low result has several possible causes.

Adult growth hormone deficiency usually requires specialist assessment and, in many cases, a stimulation test.

 

Can lifestyle changes affect IGF-1?

Nutrition, protein intake, sleep and wider metabolic health can influence IGF-1.

However, lifestyle changes will not correct an abnormal result caused by an underlying pituitary, liver or endocrine condition.

 

Can IGF-1 levels change with age?

Yes. IGF-1 generally peaks during puberty and gradually declines throughout adulthood.

Results must be assessed against an age-appropriate laboratory reference range.

 

Can IGF-1 be tested at any time of day?

IGF-1 is comparatively stable throughout the day, so timing is usually less important than it is for growth hormone.

You should still follow the instructions supplied by your testing provider.

 

What happens after a high IGF-1 result?

The test may first be repeated to confirm that the result is persistently elevated.

The next steps depend on symptoms, medical history and whether exogenous HGH is being used.

Further assessment may include growth hormone suppression testing and, where appropriate, pituitary imaging.