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Lab test explainer

IGF-1

IGF-1 is a hormone that growth hormone stimulates. Clinicians use it to evaluate the growth hormone system or to follow a treatment that affects it.

Printed on reports as: Insulin-like growth factor 1 · IGF-1 · IGF-I · Somatomedin C

What it measures

Circulating insulin-like growth factor 1. Growth hormone stimulates IGF-1 production, and because growth hormone levels vary through the day, IGF-1 is the steadier marker.

Why it is checked

To investigate a suspected growth hormone disorder, or to monitor a treatment affecting this pathway.

What can affect the result
  • Age and sex. IGF-1 is low in childhood, peaks around puberty and declines through adulthood, so the interval on your report should match your age and sex.
  • Other conditions. A published review lists several that can lower IGF-1 apart from growth hormone status: fasting, anorexia and malnutrition; diabetes, depending on its control; liver disease; kidney disease; and hypothyroidism. Severe obesity can also lower it. Treatments such as oral estrogen can change how growth hormone acts.
  • The laboratory method. Reference intervals are assay-specific, so use the interval printed on your own report and compare results from the same laboratory where possible.
Read alongside

The reason for testing, symptoms, medication history, and any additional endocrine tests the clinician recommends. A single IGF-1 value rarely stands alone.

Peptide connections

One prescribing label discusses IGF-1. It addresses IGF-1 as a safety consideration. Its glucose instruction addresses a different potential treatment effect.

Prescribing informationVerified 2026-11-06

Egrifta WR · tesamorelin

EGRIFTA WR stimulates GH production and increases serum IGF-1. The effects of prolonged elevations in IGF-1 levels are unknown. Monitor IGF-1 levels during EGRIFTA WR therapy.
Section 5.2 (Elevated IGF-1 Levels)
Role of the marker
Monitoring instruction
Formulation
For injection, 11.6 mg/vial kit
Jurisdiction
United States (FDA-approved labeling on DailyMed)
Population in the source
HIV-infected adult patients with lipodystrophy
Indication and status
Reduction of excess abdominal fat in HIV-infected adult patients with lipodystrophy. The label states it is not indicated for weight loss management and that long-term cardiovascular safety has not been established.
What this does not establish
The label addresses IGF-1 as a safety consideration because treatment raises it. It does not say that IGF-1 shows whether the treatment is working, and this page does not repeat the label's discontinuation language as a threshold for anyone.

Question to bring: “Why are we following IGF-1 in my case, and what change would prompt discussion about the treatment plan?”

Source: DailyMed →Watch the related WPF film →Search the directory →

A connection describes what a source says about monitoring. It does not show that a result makes anyone eligible for, or a candidate for, a medication.

Questions for your healthcare team

“Why are we following IGF-1 in my case, and what change would prompt discussion about the treatment plan?”

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Sources and review status

  • The MedlinePlus IGF-1 page covers age but not other confounders. The list of conditions comes from a 2019 peer-reviewed review, not a clinical guideline, and the review itself attributes some effects (for example liver disease and oral estrogen) to altered hepatic growth hormone action. A clinician or laboratory reviewer should confirm the wording and whether a more recent guideline should be cited.
  • No numeric reference intervals or standard-deviation thresholds are given here. Intervals depend on the laboratory, method, age and sex.

General education only. Bring your report, symptoms, and medication list to a qualified healthcare professional for advice about your care. Follow instructions from your lab or clinician if a result is marked critical.