An IGF-binding protein 3 test measures IGFBP-3, the main protein that carries insulin-like growth factor 1 through the bloodstream. Because growth hormone is released in brief pulses, a random growth hormone result can be difficult to interpret. IGFBP-3 changes more slowly and can offer a steadier view of growth hormone activity, especially when a child has poor growth. The test is usually interpreted with height measurements, growth velocity, bone age, IGF-1, thyroid tests, nutrition, and sometimes a growth hormone stimulation test. A low result can support concern about growth hormone deficiency, but it can also occur with undernutrition, liver disease, hypothyroidism, or chronic illness. A high result may reflect normal puberty, growth hormone treatment, or excess growth hormone. There is no single normal IGFBP-3 value for every person. Age, sex, pubertal stage, laboratory method, and clinical setting all shape the expected range.
- IGFBP-3 reflects growth hormone action more steadily than a random GH measurement.
- Results must be compared with an age- and assay-specific reference interval, often as a standard deviation score.
- A low IGFBP-3 result does not prove growth hormone deficiency by itself.
- Children with poor growth usually need IGF-1, growth records, and other testing alongside IGFBP-3.
- Fasting is often unnecessary, but follow the laboratory’s preparation instructions.
Table of Contents
- What the IGFBP-3 Test Measures
- Why the Test Is Ordered
- Preparation and Testing
- Normal Range and Age-Related Changes
- What a Low IGFBP-3 Result Can Mean
- What a High IGFBP-3 Result Can Mean
- Interpreting IGFBP-3 With Other Results
- Follow-Up and Next Steps
What the IGFBP-3 Test Measures
IGFBP-3 stands for insulin-like growth factor-binding protein 3. It is the most abundant binding protein for IGF-1 in the circulation. Most circulating IGF-1 travels in a three-part complex made of IGF-1, IGFBP-3, and a protein called acid-labile subunit. This complex protects IGF-1 from rapid breakdown and helps regulate how much IGF-1 is available to tissues.
Growth hormone, which the pituitary gland releases, stimulates the liver and other tissues to produce IGF-1 and IGFBP-3. IGF-1 carries out many of growth hormone’s effects on bone, cartilage, muscle, and metabolism. IGFBP-3 therefore serves as an indirect marker of the growth hormone–IGF system rather than a direct measure of pituitary growth hormone secretion.
That distinction matters because growth hormone levels rise and fall throughout the day. They are often very low between pulses, even in a healthy person. Exercise, sleep, stress, fasting, puberty, and blood glucose can all alter a single GH value. IGFBP-3 is more stable across the day, so it is less dependent on catching a hormone pulse at the right moment.
IGFBP-3 is not simply an inactive storage protein. It helps control the transport, half-life, and tissue delivery of IGF-1. Some IGFBP-3 actions may also occur independently of IGF-1. However, routine clinical testing mainly uses the marker as part of an assessment of growth hormone function.
The result may be reported in milligrams per liter, micrograms per milliliter, nanograms per milliliter, or another unit. Values cannot be compared safely across laboratories without checking the unit, assay, and reference interval. A number that appears “low” on one report may be within range on another because the methods and populations differ.
Why the Test Is Ordered
The most common use of IGFBP-3 testing is the evaluation of a child who is short, growing slowly, or crossing downward through height percentiles. The test can help estimate whether the growth hormone–IGF pathway is functioning as expected, but it is only one part of the assessment.
A clinician may order IGFBP-3 when a child has:
- A height well below the expected range for age and family pattern
- A reduced growth velocity over six to twelve months
- Delayed bone age
- A history of brain tumor, cranial radiation, head injury, pituitary surgery, or congenital pituitary abnormalities
- Other pituitary hormone deficiencies
- Symptoms or physical features that suggest a genetic disorder affecting growth
- An IGF-1 result that is low, borderline, or difficult to interpret
IGFBP-3 can be particularly useful in younger children. IGF-1 concentrations are naturally low in infancy and early childhood, and the lower end of the IGF-1 reference range may be difficult to distinguish from true deficiency. IGFBP-3 often has a wider measurable range at these ages, although it still cannot diagnose growth hormone deficiency alone.
The test may also be used during treatment with recombinant growth hormone. Most treatment monitoring relies more heavily on growth response, side effects, and IGF-1, but IGFBP-3 may add context when results are unexpected or when the clinician is evaluating the broader IGF system.
In suspected growth hormone excess, such as gigantism in a child or acromegaly in an adult, IGFBP-3 can be elevated. IGF-1 remains the preferred screening marker for excess GH because it is better validated for that purpose. An IGFBP-3 result should not replace an IGF-1 test or an oral glucose suppression test when acromegaly is being investigated.
Adults are less commonly tested for IGFBP-3. Adult growth hormone deficiency is usually assessed with clinical history, other pituitary deficits, IGF-1, and a validated stimulation test. A normal IGFBP-3 result does not rule out adult GH deficiency.
Preparation and Testing
IGFBP-3 is measured from a blood sample drawn from a vein. The draw itself usually takes only a few minutes. Unlike a growth hormone stimulation test, it does not require several timed samples or administration of a stimulating medicine.
Fasting is not routinely required for many IGFBP-3 assays. Still, the ordering clinician or laboratory may ask for an overnight fast when IGFBP-3 is being collected with glucose, insulin, lipids, or another test that requires fasting. Follow the instructions on the order rather than assuming that food is allowed.
Tell the clinician about medicines and supplements before testing. Important examples include:
- Recombinant growth hormone or long-acting growth hormone
- Estrogen-containing birth control or oral estrogen therapy
- Testosterone or other sex-steroid treatment
- Glucocorticoids such as prednisone
- Thyroid hormone
- Medicines used to treat acromegaly
- High-dose biotin supplements, which can interfere with some immunoassays
Do not stop prescribed medicine unless the clinician gives specific instructions. The timing of a sample in relation to a growth hormone injection may matter for treatment monitoring, especially with long-acting products. The endocrine team may standardize the day of the week or interval after injection so repeated results can be compared fairly.
A child’s test should be interpreted with an accurate height, weight, and growth chart. One height measurement is not enough to determine growth velocity. The clinician may review measurements from the previous year, parental heights, birth history, pubertal stage, nutrition, chronic symptoms, and medications. A left hand and wrist X-ray may be used to estimate bone age.
Acute illness can temporarily alter growth-related markers. If a child is recovering from significant infection, surgery, poor intake, or an inflammatory flare, the clinician may repeat the test after recovery. A technically valid laboratory result can still be misleading if it was obtained during an unusual physiologic state.
When monitoring over time, use the same laboratory when practical. Assays do not always produce interchangeable values. A sudden change after switching methods may reflect the test system rather than a true biologic change.
Normal Range and Age-Related Changes
There is no universal adult or pediatric IGFBP-3 normal range. The expected value changes markedly with age and puberty. Concentrations are relatively low in infancy, rise through childhood, usually peak during the pubertal growth spurt, and decline gradually after young adulthood.
Laboratories build reference intervals from groups of people considered healthy. A pediatric report may provide separate ranges by age and sex. Some laboratories also account for pubertal stage. Because puberty can occur at very different chronological ages, an apparently high or low value for age may make more sense when sexual maturation and bone age are considered.
Many endocrine specialists prefer a standard deviation score, also called a Z-score or SDS. This expresses how far the result lies above or below the mean for a matched reference population. An SDS near 0 is close to the average. Values below about −2 SDS or above about +2 SDS are often outside the central 95% of the reference population, but the laboratory’s own interpretation should be used.
A result within range is reassuring but not conclusive. Some people with partial or recently developed growth hormone deficiency have normal IGFBP-3. Conversely, a mildly low value may occur without pituitary disease. The result becomes more meaningful when it fits the growth pattern and other tests.
Several factors influence the reference comparison:
- Age: A value normal for a preschool child may be very low for a teenager.
- Puberty: Sex steroids increase GH secretion and raise IGF-1 and IGFBP-3.
- Sex: Some assays use sex-specific pediatric ranges.
- Nutrition: Low energy or protein intake can lower the GH–IGF response.
- Liver function: The liver produces much of circulating IGF-1 and IGFBP-3.
- Kidney function: Altered clearance and binding-protein fragments can complicate interpretation.
- Assay method: Antibodies, calibration, sample treatment, and units differ.
Do not compare a child’s result with a range found online unless the age, sex, pubertal stage, method, and unit match the laboratory report. Even then, the laboratory’s validated interval takes priority.
A common mistake is to label a value “optimal” within the normal range. There is no broadly accepted target point that is best for every healthy person. For diagnosis, clinicians look for consistency across growth data and related laboratory findings. During GH treatment, the goal is safe, appropriate growth and an IGF-1 level within the treatment target, not the highest possible IGFBP-3 value.
What a Low IGFBP-3 Result Can Mean
A low IGFBP-3 result can support reduced growth hormone action, especially when IGF-1 is also low and the child has poor growth velocity. It does not establish the cause. Several pituitary and nonpituitary conditions produce the same pattern.
Growth hormone deficiency
Growth hormone deficiency may be congenital or acquired. Congenital causes include abnormal pituitary development and gene variants that affect pituitary hormones or the GH pathway. Acquired causes include tumors, surgery, cranial radiation, inflammation, head trauma, and damage to the hypothalamus or pituitary stalk.
The strongest concern arises when a low IGFBP-3 result accompanies a falling height percentile, delayed bone age, low IGF-1, and other evidence of pituitary disease. Newborns with severe GH deficiency can have low blood glucose, prolonged jaundice, or a small penis in boys. Older children often have slow linear growth, a younger-looking face, and relatively preserved or increased body fat.
A normal IGFBP-3 result cannot fully exclude GH deficiency. Mild deficiency and adult-onset disease may not lower it enough to cross the reference limit. Diagnosis may require a growth hormone stimulation test, pituitary MRI, and evaluation of other pituitary hormones.
Undernutrition and chronic disease
Inadequate calories or protein can reduce IGF-1 and IGFBP-3 even when the pituitary produces GH. This can occur with food insecurity, restrictive eating, malabsorption, inflammatory bowel disease, celiac disease, or severe chronic illness. The body may become relatively resistant to GH during undernutrition and inflammation.
Liver disease can lower IGFBP-3 because the liver is a major source of the protein. Uncontrolled hypothyroidism can also reduce growth and lower growth-related markers. Kidney disease, poorly controlled diabetes, systemic inflammation, and prolonged glucocorticoid exposure can alter the axis in more complex ways.
These possibilities are why a low result often leads to a broader laboratory review rather than immediate GH treatment. Tests may include a complete blood count, metabolic panel, inflammatory markers, celiac screening, TSH and free T4, and other studies chosen from the history.
Rare IGF-system disorders
Some genetic conditions affect the GH receptor, IGF-1 production, acid-labile subunit, or other parts of the pathway. In GH insensitivity, GH may be normal or high while IGF-1 and IGFBP-3 are low. Acid-labile subunit deficiency can cause strikingly low circulating IGF-1 and IGFBP-3, with a growth pattern that differs from classic severe GH deficiency.
These disorders are uncommon and require specialist assessment. The pattern of birth size, facial features, head size, immune history, glucose levels, family history, and response to GH can help guide genetic or functional testing.
What a High IGFBP-3 Result Can Mean
A high IGFBP-3 result most often reflects increased growth hormone activity, normal pubertal physiology, treatment, or a reference-range mismatch. The degree of elevation and the accompanying IGF-1 result are important.
During puberty, GH secretion increases and IGFBP-3 commonly rises. A teenager who enters puberty earlier than peers may appear high on an age-only range but appropriate for pubertal stage or bone age. Conversely, a late-maturing teenager may have a lower value than peers without having GH deficiency.
Growth hormone therapy can raise IGFBP-3. The clinician reviews the dose, adherence, growth response, IGF-1 SDS, side effects, and timing of blood collection. An isolated elevated IGFBP-3 is not usually used as the sole reason to change treatment. Persistent elevation with a high IGF-1 result may prompt a dose review, particularly if there are headaches, swelling, joint symptoms, glucose changes, or other adverse effects.
Excess endogenous GH can elevate both IGF-1 and IGFBP-3. In a child with unusually rapid growth, enlarged hands or feet, headaches, sweating, or coarse facial changes, the clinician may evaluate for pituitary gigantism. In adults, acromegaly may cause changes in facial features, ring or shoe size, sweating, joint pain, sleep apnea, hypertension, or diabetes. IGF-1 is the main screening test, followed when needed by an oral glucose growth hormone suppression test.
Kidney dysfunction may produce increased or difficult-to-interpret IGFBP-3 measurements because binding proteins and fragments accumulate. Some assay antibodies detect fragments differently. A high laboratory number in advanced kidney disease does not necessarily mean that biologically active IGF signaling is excessive.
An unexpectedly high result should first be checked against the correct demographic range and unit. The clinician may repeat the sample, confirm IGF-1, review supplements and medications, and ask whether the laboratory method changed. Testing for a pituitary tumor is based on the full clinical and biochemical picture, not IGFBP-3 alone.
Interpreting IGFBP-3 With Other Results
IGFBP-3 is most useful when it is interpreted as one piece of a coordinated evaluation. The following patterns illustrate common possibilities, but they are not diagnostic rules.
| IGFBP-3 pattern | Other findings | Possible interpretation |
|---|---|---|
| Low | Low IGF-1, slow growth, delayed bone age | GH deficiency is possible; nutrition, thyroid, liver, and chronic disease causes must also be assessed. |
| Low | Low IGF-1, normal or high GH | Undernutrition, inflammation, liver disease, or GH resistance may be considered. |
| Normal | Low IGF-1 and poor growth | GH deficiency is not excluded; review age, nutrition, assay, and whether stimulation testing is appropriate. |
| High | High IGF-1 and rapid growth or acromegaly features | GH excess may be present and requires dedicated confirmation. |
| High | Pubertal child with normal growth pattern | May be a normal pubertal rise, especially if the range does not account for maturation. |
| Rising during treatment | Improved growth and IGF-1 within target | Often an expected treatment response; continue safety and growth monitoring. |
IGF-1 is usually the more sensitive screening marker across older childhood and adulthood. IGFBP-3 may add information in very young children, in suspected severe deficiency, or when IGF-1 is borderline. Neither marker can distinguish every child with GH deficiency from children who are short for other reasons.
Growth velocity often carries more weight than one laboratory value. A child who remains on a low but stable percentile and grows at an age-appropriate rate may have familial short stature. A child who drops through percentiles deserves evaluation even if IGFBP-3 falls within range.
Bone age adds another layer. Delayed bone age occurs in GH deficiency, hypothyroidism, undernutrition, chronic disease, and constitutional delay of growth and puberty. It does not identify the cause by itself. Pubertal examination is equally important because delayed puberty can lower GH-related markers and blunt a stimulation-test response.
If a stimulation test is performed, the peak GH cutoff depends on the stimulating agent, assay, age, body composition, and local protocol. A result should not be interpreted with a cutoff copied from another laboratory. Some children require sex-steroid priming before testing to reduce false-positive diagnoses related to delayed puberty, although practice varies.
Pituitary MRI may be appropriate when biochemical and growth findings strongly suggest deficiency, when several pituitary hormones are low, or when neurologic symptoms are present. Imaging should support a clinical diagnosis rather than replace hormone testing.
Follow-Up and Next Steps
The next step after an abnormal IGFBP-3 result depends on the reason for testing. A mild isolated abnormality often leads to confirmation and review rather than urgent treatment. The clinician may repeat IGFBP-3 and IGF-1 using the same laboratory, correct a nutrition or thyroid problem, and track growth for several months.
For a child with poor growth, a thorough plan commonly includes:
- Confirming accurate serial height and weight measurements.
- Calculating growth velocity and comparing height with parental expectations.
- Reviewing birth history, nutrition, bowel symptoms, chronic disease, sleep, and medications.
- Checking IGF-1, thyroid function, blood count, metabolic tests, and condition-specific screening.
- Assessing pubertal stage and obtaining bone age when useful.
- Referring to pediatric endocrinology when growth is markedly slow, laboratory findings are concerning, or pituitary disease is possible.
- Considering GH stimulation testing, MRI, or genetic testing only when the combined evidence supports it.
Seek prompt medical assessment when poor growth is accompanied by severe headaches, vomiting, vision changes, excessive thirst and urination, recurrent low blood glucose, delayed or regressing puberty, or signs of multiple pituitary deficiencies. These features can point to a structural or broader endocrine problem.
During GH treatment, monitoring is individualized. Clinicians follow height velocity, pubertal progression, IGF-1, glucose risk, thyroid function, adherence, and adverse effects. Severe headache with vomiting or visual symptoms, a limp or hip pain, marked swelling, breathing problems during sleep, or worsening scoliosis should be reported promptly. These symptoms do not always mean treatment caused a complication, but they need evaluation.
A single IGFBP-3 result should not determine whether someone receives growth hormone. Treatment is appropriate only for defined conditions after a complete assessment. Giving GH to raise a laboratory number without a supported diagnosis can expose a person to cost, injections, and adverse effects without predictable benefit.
References
- Establishment of IGF-1 and IGFBP-3 continuous reference intervals in healthy children and adolescents 2024 (Original Research)
- Disorders of Growth Hormone in Childhood 2022 (Review)
- Growth and Growth Disorders 2025 (Review)
- Testing for growth hormone deficiency in children 2020 (Review)
- Advances in differential diagnosis and management of growth hormone deficiency in children 2021 (Review)
Disclaimer
IGFBP-3 results require interpretation with the laboratory’s age-specific range, growth history, and related tests. This information is educational and cannot diagnose growth hormone deficiency or guide treatment for an individual child or adult. Discuss abnormal results and growth concerns with a qualified clinician or endocrinologist.
