This test measures levels of Insulin-Like Growth Factor 1 (IGF-1) using liquid chromatography–mass spectrometry (LC/MS), one of the most accurate and specific testing methods available. IGF-1 plays a critical role in growth, metabolism, and cellular repair, and its levels reflect growth hormone (GH) activity in the body.
Why Is IGF-1 Testing Important?
IGF-1 testing is used to:
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Evaluate growth disorders in children and adults
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Diagnose and monitor acromegaly (excess growth hormone)
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Support diagnosis of growth hormone deficiency (GHD)
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Guide and monitor GH or IGF-1 replacement therapy
Clinical Insights
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High IGF-1 levels may indicate acromegaly, a condition where the body produces too much growth hormone. IGF-1 levels are used both for diagnosis and to monitor treatment after surgery or with medications (e.g., somatostatin analogs, pegvisomant).
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Low IGF-1 levels may suggest growth hormone deficiency (GHD), especially in individuals with multiple pituitary hormone deficiencies or genetic conditions.
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IGF-1 is also useful in adjusting GH replacement therapy in both children and adults.
Why LC/MS Testing Is Superior
Most IGF-1 tests use immunoassays, which can give inaccurate results due to interference from IGF binding proteins (IGFBPs). LC/MS testing offers several advantages:
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Highly specific: Accurately measures intact IGF-1, minimizing interference from IGFBPs.
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Sensitive and reliable: Offers excellent precision with a coefficient of variation (CV) ≤5%.
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Detects rare IGF-1 variants, which may be missed by immunoassays.
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Standardized to WHO reference materials for consistent, comparable results.
Note: LC/MS may yield lower IGF-1 levels than traditional immunoassays. This is due to technical differences, not necessarily a reflection of true biological variance. Always use the same method consistently for monitoring over time.
Who Should Be Tested?
This test is appropriate for individuals who may have:
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Short stature or delayed growth in children
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Gigantism or acromegaly symptoms (enlarged hands/feet, facial changes)
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Pituitary tumors or prior pituitary surgery
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Suspected adult growth hormone deficiency (especially with panhypopituitarism)
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Ongoing GH or IGF-1 therapy needing dosage adjustment
How the Test Works
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Sample Type: Serum
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Method: High-resolution LC/MS with isotope-labeled internal standards
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Analytical Range: 10–2,000 ng/mL
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Reference Ranges: Adjusted by age and sex, based on data from over 2,000 individuals
This method dissociates IGF-1 from its binding proteins and recovers nearly 100% of total IGF-1 for accurate measurement.
Understanding Your IGF-1 Results
Results are interpreted using Z-scores, which compare your IGF-1 level to the average for your age and sex.
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Z > +2.0: Suggests GH excess (e.g., acromegaly or over-treatment)
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Z between -2.0 and +2.0: Normal IGF-1 level
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Z < -2.0: Suggests GH deficiency or under-treatment
A normal IGF-1 level does not fully exclude acromegaly or GHD. Follow-up testing (e.g., glucose suppression or GH stimulation) may be required in some cases.
Key Considerations
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Stay consistent: Use the same assay method over time to monitor treatment.
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Don’t switch platforms without consulting your provider, as values may differ significantly between LC/MS and immunoassays.
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Rare IGF-1 variants, if present, are reported separately and may affect interpretation but are uncommon (<1% prevalence).
IGF 1, LC/MS
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