What can an IGF-1 test tell you?
An IGF-1 test does not diagnose a condition on its own, but it can provide key clues about GH activity. Here’s what you can expect it to illuminate:
Evaluate for GH excess. Persistently high, age-adjusted IGF-1 suggests GH overproduction, which can cause a disorder called acromegaly, which is characterized by tissue growth and metabolic dysfunction.
Evaluate for GH deficiency in adults. Low IGF-1 may support possible GH deficiency, but provocative (stimulation) testing is usually required to confirm the diagnosis in adults.
Monitor known pituitary disorders. IGF-1 testing helps evaluate GH function in people with pituitary disease and can reflect the degree of GH deficiency or excess. It can also be a first step in testing for certain hormone-producing pituitary tumors.
Because IGF-1 levels vary significantly with age, sex, and pubertal stage, many labs also report a Z-score alongside the lab result. The Z-score shows how your IGF-1 level compares to others in your age group, measured in standard deviations:
Z-score around 0. This score means your IGF-1 is typical for your age.
Z-score greater than +2.0. This score may signal growth hormone excess, which can be a sign of acromegaly or overtreatment with GH.
Z-score lower than −2.0. This score may point to GH deficiency, although additional GH stimulation tests are often needed for confirmation.
It’s also possible for some people with small GH-secreting pituitary tumors or higher body mass index to have normal IGF-1 despite underlying GH-related issues, so providers interpret Z-scores alongside symptoms, imaging, and other labs.
What is being tested?
IGF-1 is a hormone that carries out many of growth hormone’s effects in the body, helping to build muscle, strengthen bones, and support healthy metabolism. The liver is primarily responsible for producing IGF-1, which happens after the pituitary gland releases GH. IGF-1 also acts directly in tissues like muscle, bone, and cartilage to promote growth and repair through cell signaling pathways. Most IGF-1 in the bloodstream is bound to specific proteins, mainly IGFBP-3, which help control how much is available to tissues.
Together, GH and IGF-1 form a feedback loop that keeps growth and metabolism in balance. When IGF-1 levels are too high, tissues can grow excessively, as in the disorder acromegaly. When they’re too low, growth and bone strength can suffer, as in GH deficiency. Because IGF-1 levels change with age and sex, results are compared against adjusted reference ranges.
Where is the IGF-1 test typically included?
IGF-1 is not part of standard metabolic panels. It’s commonly ordered:
As a single test. When a provider suspects acromegaly or GH deficiency.
Within a pituitary hormone panel. Along with prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone, thyroid-stimulating hormone (TSH), free thyroxine (T4), and morning cortisol.
After treatment for acromegaly. To assess whether biomarkers like IGF-1 and GH are back within the normal range.
Who should get an IGF-1 test?
A provider may order an IGF-1 test if you have symptoms related to GH excess or GH deficiency.
Signs and symptoms of GH excess include:
Enlarged hands or feet, or a change in ring or shoe size
Jaw or brow growth
Larger lips, nose, or tongue
Skin thickening
Excessive sweating
Deeper voice
Skin tags
Headaches
Vision problems
Joint pain
Carpal tunnel symptoms
Loud snoring or sleep apnea
Signs and symptoms of GH deficiency in adults include:
When pituitary disease is suspected or confirmed, IGF-1 testing can help guide next steps, including follow-up testing, imaging, or specialist care.
