How it is used
- Screening when growth hormone deficiency or excess is suspected
- Monitoring response in people already on therapy
- Interpreted against age- and sex-specific reference ranges
Why a single value is rarely conclusive
IGF-1 is affected by age, nutrition, liver and kidney function, thyroid status, oral estrogen and acute illness. Assays also vary between laboratories.
Providers may combine IGF-1 with clinical history, other laboratory tests and, in some cases, stimulation testing.
What it is not
IGF-1 is not a general wellness score, and results should not be self-interpreted or used to self-treat. Testing and interpretation belong with a licensed provider.