Growth Hormone Blood Test

What this test measures

Growth hormone, also called somatotropin, is produced by the pituitary gland and acts on many tissues. It supports linear growth in children and helps regulate body composition, muscle, bone, and glucose metabolism in adults. Too little or too much growth hormone can cause distinct patterns of symptoms, which is why it is measured when a disorder is suspected.

Because growth hormone is released in pulses rather than at a steady level, a random blood sample may be low or high without indicating a real problem. Laboratories often compare the result with a reference range, and providers may order stimulation or suppression testing to see how the pituitary responds under controlled conditions. IGF-1 is frequently measured as a steadier indicator of growth hormone activity.

This test may be ordered for a child whose growth is slower or faster than expected, for an adult with features suggesting growth hormone excess or deficiency, or during follow-up of pituitary disease. Results are interpreted with age, sex, symptoms, other hormone levels, and imaging when relevant. A qualified healthcare provider should make the diagnosis and discuss any next steps.

• Growth hormone (somatotropin) level
• Growth hormone concentration in ng/mL
• Growth hormone response during a stimulation test when ordered
• Growth hormone suppression during a glucose protocol when ordered
• Insulin-like growth factor 1 (IGF-1) when paired
• IGF-binding protein 3 (IGFBP-3) when paired
• Other pituitary hormone markers when a panel is included

Why people order this test

• Evaluate slow or unusual growth in a child
• Investigate features that suggest growth hormone excess in an adult
• Support the assessment of suspected growth hormone deficiency
• Follow known pituitary disease or treatment
• Pair with IGF-1 for a steadier view of growth hormone activity
• Add context when other pituitary hormone tests are abnormal

How to prepare

Some growth hormone protocols require fasting, a morning collection, or a period of rest before sampling. Follow the collection instructions provided by the laboratory, and tell the testing provider about any medications you take, since some affect growth hormone levels.

Understanding your results

Results are typically available within one to three business days. A single growth hormone level can be difficult to interpret because of the hormone's natural bursts, so providers usually review it with IGF-1, other hormone tests, and the clinical picture. A qualified healthcare provider can explain what the numbers mean in a specific case.