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Growth Hormone (GH)

A hormone from the pituitary gland that drives growth in children and helps manage body composition in adults. It is released in bursts, so one level is hard to interpret.

AI-verified against cited sources. Awaiting expert reviewAlso called GH, hGH, HGHLOINC 2963-7

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What it is

Growth hormone (GH) is made by the pituitary gland at the base of the brain. It helps children grow, and in adults it helps maintain muscle and bone and affects how the body uses fat and sugar. GH is released in short bursts, mostly during deep sleep and in response to exercise, low blood sugar or a protein-rich meal. Between bursts, levels can fall to almost nothing. In the liver, GH signals the release of IGF-1, which carries out many of its effects.

Why it matters

Clinicians check growth hormone when they are looking at how well the pituitary gland is working, slow growth in a child, or signs of too much GH in an adult (acromegaly). Because levels swing so much, one random result usually can't answer those questions. Clinicians more often use IGF-1, which stays steadier, or measure GH at set times after a sugar drink or a stimulating test (suppression and stimulation tests). The Endocrine Society's acromegaly guideline recommends IGF-1 as the first test for this reason.

If it’s low

A low or undetectable random result is common in healthy people, because GH is released in bursts with long gaps between. A single low level can't show whether you make too little GH. Clinicians use IGF-1 and, when needed, a stimulation test for that question. For adults, the Endocrine Society says confirmation with stimulation testing is usually needed.

Common causes

  • The long gaps between normal GH pulses
  • Older age, since GH falls with age. Body mass index also influences GH
  • Pituitary or hypothalamic conditions, such as a pituitary tumor or its treatment (uncommon)

What can help

  • Ask whether IGF-1 is a better first test for your question
  • Ask whether stimulation testing is worth discussing, and whether it should be done in an endocrine testing center

If it’s high

A random result above your lab's range often reflects the natural pulses of GH, so it is not a cause for concern on its own. Sleep, exercise, fasting, low blood sugar, stress and a recent protein meal can all push it up. Long-term poor nutrition, kidney failure and liver cirrhosis can also raise baseline GH. Less often, a high level is linked to too much GH from a pituitary tumor (acromegaly in adults, gigantism in children). Clinicians look into that with IGF-1 and a glucose suppression test, not with one random level.

Common causes

  • A natural GH pulse, for example after deep sleep, exercise or a protein-rich meal
  • Low blood sugar, stress or a long overnight fast
  • Sex hormones, including estrogen, which influence GH release and are one reason intervals differ between men and women
  • Poor nutrition, anorexia or starvation, kidney failure or liver cirrhosis
  • A GH-making pituitary tumor (acromegaly or gigantism) (uncommon)
  • GH made by a tumor outside the pituitary gland (rare)

What can help

  • Ask your clinician whether IGF-1 or a glucose suppression test would answer your question better than a random level
  • Tell your clinician about sleep, exercise, fasting and any biotin supplement before the draw
  • Ask whether to repeat the test fasting and after 30 minutes of rest

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on sex and age. Choose women or men to see the one that applies.

Children and teens 5 ranges

See Growth hormone by age and sex, with the U.S. survey numbers where they exist.

What can affect your result

  • Sleep, exercise, fasting, low blood sugar, stress and protein-rich meals
  • Age, sex and body mass index
  • Sex hormones, including estrogen
  • Nutrition, kidney function and liver function
  • Time of day: GH is released in pulses, with more during deep sleep
  • Assay and calibration standard: results from different labs aren't interchangeable
  • High-dose biotin and some medicines (such as asfotase alfa) can interfere with some assays
  • Not fasting or not resting: sleep, exercise, low blood sugar, stress and protein-rich meals trigger GH release in the hours before a draw.
  • High-dose biotin (vitamin B7) can interfere with some assays. Labcorp advises stopping biotin at least 72 hours before the draw unless your clinician says otherwise.
  • Asfotase alfa (Strensiq) can falsely raise results on some assays. Quest suggests an alternate method for people who take it.
  • Rarely, antibodies to animal proteins (HAMA or heterophile antibodies) can distort an immunoassay result (Mayo).
  • Calibration changed from the older pituitary-derived standard (80/505) to a recombinant one (98/574), which lowered results by about 25% (ARUP). Keep to one lab when following trends.

After fasting and at least 30 minutes of rest (Labcorp, Quest). Mayo requires 8 hours of fasting. GH is released in pulses, with more during deep sleep, so timing matters. A single level is a snapshot. GH has a half-life of about 20 to 25 minutes (Labcorp), so a result reflects the last few minutes to hours.

When to talk to a clinician

There is no emergency threshold for growth hormone, and one result outside your lab's range is not urgent. Talk with the clinician who ordered the test, especially if you notice your hands or feet growing, your facial features changing, new joint pain or headaches, or if a child is growing slowly. For reference, in a glucose suppression test ARUP notes that healthy people have GH below 1 ng/mL within 2 hours of a 75 or 100 gram glucose dose.

Questions you could ask

  • Which test is best for my question: a random GH, IGF-1, or a timed test?
  • Should follow-up tests use the same lab and method?
  • Could sleep, exercise, fasting or stress before the draw explain this result?
  • Would IGF-1 or a glucose suppression test tell us more than a random level?
  • Should this be repeated fasting and after resting?
  • Is a low random level expected, given how GH is released?

Questions people ask

Why is one growth hormone result hard to interpret?

GH is released in bursts, mostly during deep sleep and after exercise. Between bursts it can fall almost to zero. A single sample can catch a peak or a gap, so it rarely answers a clinical question. IGF-1 and timed tests after a sugar drink or a stimulating test are used instead.

Why do labs print such different ranges?

Labs use different assays and calibration standards, and they build their ranges from different groups. For adults the upper limit ranges from under 1 ng/mL to 10 ng/mL across labs. Switching to a newer calibration standard also lowered results by about a quarter. Compare your result with the range on your own report.

How do I convert the units?

1 ng/mL is the same as 1 µg/L. Some labs report in mIU/L. On the current calibration standard, multiply ng/mL by 3 to get mIU/L, so 1 ng/mL is about 3 mIU/L.

Show the science and sources

Units

  • 1 ng/mL = 1 ng/mL
  • 1 ng/mL = 1 µg/L
  • 1 ng/mL = 3 mIU/L

Open the Growth hormone unit converter

For clinicians and researchers

GH is a peptide hormone from the anterior pituitary. The 22 kDa form is the most abundant, followed by a 20 kDa splice variant, and about half of circulating GH is bound to a high-affinity binding protein (Labcorp). Secretion is pulsatile, with a half-life of about 20-25 minutes (Labcorp), and is stimulated by exercise, deep sleep, hypoglycemia and protein ingestion (Mayo). Labcorp notes an individual's level can range from undetectable to raised across a day. Single measurements have limited value (Mayo, Labcorp, Quest). Assays are not interchangeable: Mayo uses the Beckman Access ultrasensitive hGH immunoassay; Labcorp's serum test uses the IDS-iSYS assay, which is specific for the 22 kDa form, shows no cross-reactivity with pegvisomant and is calibrated to the WHO recombinant standard 98/574. The move from the pituitary-derived standard 80/505 to 98/574 lowered results by about 25% (ARUP, LifeLabs), and on the newer standard 1 µg/L equals about 3 mIU/L (Chinese University of Hong Kong); older calibrators used a different factor. Reference intervals therefore differ by lab, assay and sex, from upper limits under 1 ng/mL in men at Mayo to 10 ng/mL at Labcorp. The Endocrine Society acromegaly guideline (2014) recommends IGF-1 as the initial test, advises against routine single random GH measurements because secretion is episodic, and confirms the diagnosis by failure of GH to suppress after an oral glucose load. ARUP cites GH below 1 ng/mL within 2 hours of a 75 or 100 g glucose dose in healthy subjects. Mayo reports a nadir below 0.3 ng/mL in normal subjects after 75 g of glucose, and a nadir cutoff of 0.53 ng/mL that separated remission from active acromegaly on its assay. For deficiency, the Endocrine Society 2011 guideline says confirmation with stimulation testing is usually required unless there is a proven genetic or structural lesion persisting from childhood, and ARUP notes expected adult peak GH depends on the stimulation test used. A 2024 review adds that random GH and IGF-1 are not reliable alone for adult GH deficiency. Mayo recommends IGF-1 by mass spectrometry as the first test for judging growth in children.

LOINC 2963-7 (primary), 25529-9, 33858-2. Specimen: serum.

Sources

  1. HGH: Growth Hormone, Serum, Mayo Clinic Laboratories
  2. Growth Hormone (GH) (test code 521), Quest Diagnostics
  3. Growth Hormone (test 004275), Labcorp
  4. Endocrinology Expected Values and S.I. Unit Conversion Tables (Growth Hormone, ICMA, test 500647), Labcorp (Endocrine Sciences)
  5. Growth Hormone (GH), Michigan Medicine Laboratories (MLabs)
  6. Growth Hormone Method Update and Reference Range Change, LifeLabs (Canada)
  7. Growth Hormone (ARUP test 0070069), ARUP Laboratories
  8. Growth Hormone (GH), Serum (Ward Manual), Department of Chemical Pathology, The Chinese University of Hong Kong
  9. Acromegaly: An Endocrine Society Clinical Practice Guideline, Journal of Clinical Endocrinology & Metabolism (2014)
  10. Acromegaly diagnosis, treatment guideline issued by the Endocrine Society, Healio (2014)
  11. Evaluation and Treatment of Adult Growth Hormone Deficiency: An Endocrine Society Clinical Practice Guideline, Journal of Clinical Endocrinology & Metabolism (2011)
  12. A 2024 Update on Growth Hormone Deficiency Syndrome in Adults: From Guidelines to Real Life, Journal of Clinical Medicine (2024)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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