IGF-1 Test (Insulin-like Growth Factor 1)
An IGF-1 test measures insulin-like growth factor 1, a hormone the liver makes in response to growth hormone. Because growth hormone itself is released in short bursts, IGF-1 gives clinicians a steadier way to look at that system.
About this test
Growth hormone is released by the pituitary gland in pulses, mostly overnight, which makes it awkward to measure directly — two samples taken hours apart can look completely different for reasons that have nothing to do with health. IGF-1 solves that problem.
This version is run by liquid chromatography with mass spectrometry, an analytical method valued for its specificity. It separates the molecule of interest from other substances in the sample before measuring it, which reduces the interference that can affect immunoassay-based methods.
Who might consider this test?
- Clinicians order IGF-1 when they are evaluating growth hormone activity
- in children and adolescents whose growth is being followed, and in adults where a pituitary question is being explored.
- It is also used to follow a known situation over time under a clinician's care, since IGF-1 is stable enough to compare across visits.
Test details
| Quest code | 16293 |
|---|---|
| Methodology | Liquid Chromatography/Mass Spectrometry |
| Sample type | 0.5 mL serum |
| Collection | Quest patient service center |
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Additional details
Why IGF-1 rather than growth hormone
Measuring growth hormone directly means catching a hormone that comes in waves. A sample drawn between pulses can look very different from one drawn during a pulse, and neither tells you much on its own without specialized timed testing.
IGF-1 smooths that out. It reflects growth hormone activity over a longer period and holds steady enough through the day that one sample is generally informative. That practicality is why it has become the routine first marker for this system.
What influences the measurement
IGF-1 changes substantially with age — it is highest during adolescence and declines gradually through adult life — so results are always interpreted with age and sex in mind. Nutrition matters too: extended undernutrition lowers IGF-1, as can liver disease, since the liver is where most of it is produced.
Some medications and medical conditions also shift the result. Because so many ordinary factors move this marker, a clinician reviews it alongside your history rather than treating one measurement as a verdict about anything.
Markers commonly reviewed with it
Depending on the question, a clinician may look at IGF binding protein 3, thyroid markers, prolactin, cortisol, or sex hormones alongside IGF-1. Each of those touches the same pituitary and metabolic system from a different angle, and the pattern is more informative than one result standing alone.
If a clinician is evaluating pituitary function specifically, more involved dynamic testing may be part of that process. This blood test is a starting point in such an evaluation, not a substitute for it.
Ordering, pricing, and collection
The cash price shown next to the order button covers the laboratory test and the physician's order, with no insurance claim and no separate consultation fee. Collection takes a few minutes at a Quest patient service center, usually without an appointment, and your report is delivered securely to you for review with a clinician.
Order online and a physician order is included — no doctor's visit and no insurance needed. Your sample is collected at a Quest Diagnostics patient service center.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What does an IGF-1 test measure?
It measures insulin-like growth factor 1, a hormone the liver produces in response to growth hormone. Because it stays relatively steady through the day, it reflects growth hormone activity better than a single growth hormone measurement would.
Why not just measure growth hormone?
Growth hormone is released in pulses, mostly overnight, so a single sample can be misleading. IGF-1 reflects activity over a longer period, which makes one routine blood draw far more informative.
How much does an IGF-1 test cost?
The cash price is listed next to the order button on this page and includes the physician's order. No insurance is billed and there is no separate doctor's visit charge.
Does age affect IGF-1?
Yes, considerably. IGF-1 is highest during adolescence and declines through adult life, so results are always interpreted with age and sex in mind by a clinician.
What does LC/MS mean on this test?
Liquid chromatography with mass spectrometry is an analytical method that separates the molecule being measured from other substances in the sample first, which improves specificity compared with some immunoassay methods.
Do I need to fast?
No preparation instructions are listed for this test, though people follow any instructions their ordering clinician provides. Follow whatever instructions your ordering clinician gives, particularly if other tests are collected at the same visit.