Growth hormone (GH)
Pituitary hormone that affects growth, metabolism, bones and muscles
Also known as
Definition
Growth hormone (GH, somatotropin) is made in the pituitary gland at the base of the brain. In children it mainly drives bone growth, muscle development and height; in adults it affects bones, muscles and metabolism. GH is released in pulses whose size and duration vary with time of day, age and sex; diet and activity also play a role. That is why a single blood value is rarely informative.
| Parameter | Value |
|---|---|
| Unit | ng/ml (µg/l) |
| Reference Range | Typical for adults in a single measurement: men 0.05–3 ng/ml, women 0.05–8 ng/ml. Labs vary; the reference range on your own report is what counts. Discuss any deviation with your doctor. |
Agree on your personal target range with your doctor.
1 ng/ml equals 1 µg/l; the number stays the same.
↓ What a low value means
A low single value can be normal if the sample was taken at the end of a pulse. A deficiency is therefore checked with a stimulation test: if GH does not rise enough after a stimulating medicine, this can point to GH deficiency. Low levels can be linked to an underactive pituitary gland, in which other hormones may also be low. In adults, a deficiency can come with lower bone density and muscle mass, fatigue and changes in cholesterol levels. Discuss your result with your doctor.
↑ What a high value means
A high single value can be normal if the sample was taken during a pulse. An excess is therefore checked with a suppression test: if GH does not fall enough after drinking a glucose solution, this can point to GH excess. In adults this is called acromegaly, in children gigantism; the most common cause is a tumor in the pituitary gland. High levels can also be linked to GH resistance. Discuss any deviation with your doctor.
When to test
GH tests are ordered for symptoms that suggest a deficiency or excess, or to monitor treatment. They are uncommon in adults, because symptoms such as fatigue usually have other causes. Instead of a single measurement, stimulation or suppression tests with several blood samples over about two hours are used; IGF-1 is often measured as well. Fasting may be needed before the test.
Frequently asked questions
Why does a single GH value tell so little? +
GH is released in pulses whose size and duration vary with time of day, age and sex. Depending on whether the sample was taken during or after a pulse, a high or a low value can be normal. Stimulation or suppression tests are more informative.
What is the difference between GH and IGF-1? +
IGF-1 carries part of GH's effect in the body. Unlike GH, IGF-1 stays relatively stable throughout the day. That is why measuring IGF-1 is considered a reliable way to track the GH axis. Sometimes IGFBP-3, the main carrier protein of IGF-1, is measured as well.
How does a stimulation or suppression test work? +
In a stimulation test, blood is drawn first, then you receive a medicine through an IV line that prompts the pituitary to release GH; further blood samples follow over the next two hours. In a suppression test, you drink a glucose solution, and blood is drawn every 30 minutes for two hours to see whether GH falls.
Is GH measured routinely in adults? +
No. GH tests are fairly uncommon in adults, because symptoms such as fatigue or declining muscle mass usually have other causes. They are mainly considered when a pituitary disorder is suspected. Whether a test makes sense for you is something to clarify with your doctor.
Growth hormone (GH)
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.