Also Known As
Human Growth Hormone (HGH)
Formal Name
Growth Hormone
This article was last reviewed on
This article waslast modified on 26 November 2018.
At a Glance
Why Get Tested?

To identify diseases and conditions caused by either a deficiency or overproduction of growth hormone (GH), to evaluate pituitary function, and to monitor the effectiveness of GH treatment

When To Get Tested?

As part of an evaluation of pituitary function. Slow growth in stature, delayed development (in children), decreased bone density and/or muscle strength, and increased lipids (in adults) all could be related to insufficient GH production. Symptoms suggestive of gigantism in children or acromegaly in adults may be a result of excess GH production

Sample Required?

Usually several blood samples are taken at timed intervals from veins in your arm. Sometimes a single sample of blood is required following a fast or after a period of strenuous exercise

Test Preparation Needed?

In healthy adults, GH levels remain stable, but rise sharply 3-4 hours after a meal and within 60 minutes after the onset of sleep. One sample should therefore be taken fasting.

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you will be able to access your results online.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, gender, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

Growth hormone (GH) is essential for a child’s normal growth and development and promotes proper long bone growth from birth through puberty. Children with insufficient GH production grow more slowly and are smaller in size for their age; one of the first symptoms of growth hormone deficiency (GHD). It should be noted that short stature in itself can also be related to familial traits or other genetic disorders.  Constitutional delay (i.e. temporary delay in growth) is the most common cause of short stature in childhood.

Excess GH is most often due to a benign GH-secreting pituitary tumour. Too much GH can cause children’s long bones to continue to grow beyond puberty, resulting in gigantism with heights of over 2.1 meters. Those with excess GH may also have thickening of facial features, general weakness, delayed puberty, and headaches. 

Although GH is not as active in adults, it does play a role in regulating bone density, muscle mass, and lipid metabolism. Deficiencies can lead to decreased bone densities, lower muscle mass, and altered lipid concentrations. Excess GH in adults can lead to acromegaly, marked not by bone lengthening but by bone thickening. Although symptoms such as skin thickening, sweating, fatigue, headaches, and joint pain can be subtle at first, increased GH concentrations can lead to enlarged hands and feet, enlarged facial bones, carpal tunnel syndrome (trapped nerves), and abnormally enlarged internal organs. If untreated, acromegaly in adults and gigantism in children can lead to complications such as type 2 diabetes, increased cardiovascular disease risk, high blood pressure, arthritis, and in general, a decreased life span. GH stimulation and suppression tests are most often used to diagnose GH abnormalities. Since growth hormone is released by the pituitary gland in bursts throughout the day, random measurements of GH levels are not usually of use clinically.

How is the sample collected for testing?

Usually GH suppression or stimulation testing is done. After you have fasted for 10 to 12 hours, a blood sample is taken from a vein in your arm. Under medical supervision, you are then given either a standard glucose solution to drink (for a suppression test), or you are given an intravenous (IV) injection of a solution of insulin, glucagon, arginine or GHRH (for a stimulation test) through a vein in your arm. Blood samples are then taken from your veins at timed intervals. GH tests are performed on each sample collected to monitor the change in levels of growth hormone over time.

Since GH is released by the pituitary in bursts, random GH levels are not very useful. Sometimes a single sample of blood is taken following a fast or after a period of strenuous exercise is used as a screening test for growth hormone deficiency. In the event of the GH level being low, the above more definitive tests are required to confirm deficiency. A normal/raised growth hormone result effectively excludes growth hormone deficiency.

Is any test preparation needed to ensure the quality of the sample?

In healthy adults, GH levels remain stable, but rise sharply 3-4 hours after a meal and within 60 minutes after the onset of sleep. One sample should therefore be taken fasting.

Accordion Title
Common Questions
  • How is it used?

    GH testing is not used as screening test. It is primarily requested on those with symptoms of growth hormone abnormalities, as a follow-up to other abnormal hormone test results, or to help understand how the pituitary gland is working.

    Periodic GH measurements (as part of a stimulation test) may also be performed on children who have had radiation treatment of the central nervous system or whole body irradiation prior to stem cell transplants. This is common in Acute Lymphoblastic Leukaemia (ALL) where irradiation of the brain can affect the hypothalamus and pituitary gland, thus affecting growth.

    Growth hormone tests help identify excess and diminished GH production and give your doctor information about the severity of your condition. The tests are part of the diagnostic workup required to find a cause for abnormal hormone production. Testing most often involves either a GH stimulation test or a GH suppression test to track GH levels over time.

    • GH stimulation tests help to diagnose hypopituitarism.  For a stimulation test, a sample of blood is taken after you have fasted for 10-12 hours.  Then, under close medical supervision, you are given an intravenous solution of either insulin, glucagon or arginine. Blood samples are then taken at timed intervals and GH levels are tested in each to see if your pituitary gland was stimulated by the insulin (or glucagon/arginine) to produce expected levels of GH.
    • GH suppression tests help to diagnose hyperpituitarism, which in addition to other blood tests and imaging scans, can help identify and locate pituitary tumours. For a suppression test, a sample of blood is taken after you have fasted for 10-12 hours.  After this you are given a standard glucose solution to drink.  Blood samples are taken at timed intervals and GH levels are tested in each to see if your pituitary gland is sufficiently suppressed by the dose of glucose.

    Often other blood tests that reflect pituitary function, such as T4, TSH, Cortisol, FSH, LH, and testosterone (in men), are also requested. These tests are usually performed prior to GH testing to make sure that they are normal and/or controlled with medication before GH testing is done. Glucose levels are measured on the samples collected during the GH suppression test, to follow glucose levels, and to make sure that the patient’s system is sufficiently challenged by the glucose solution.

    IGF-1 (Insulin-like growth factor – 1) is often measured once during GH provocation testing and is often used by itself or with GH as a monitoring tool. Produced in the liver, IGF-1 mirrors GH excesses and deficiencies but its level is stable throughout the day – making it a useful indicator of average GH levels.

    IGF-1 levels are often monitored for extended periods of time following treatment for GHD, gigantism, and acromegaly. GH and IGF-1 levels are also monitored following surgery, drug treatment, and/or radiation for a pituitary tumour.

  • When is it requested?

    GH stimulation testing is requested when your child has symptoms of GHD, such as when:

    • Your child's growth rate slows down in early childhood and (s)he is significantly shorter than others of similar age
    • TSH tests show that your child is not hypothyroid (low thyroid concentrations in the bloodstream can also cause slowed growth)
    • X-rays show delayed bone development
    • Your doctor suspects that your child’s pituitary gland is underactive
    • To monitor GH levels in children who have received radiation therapy.

    Once GHD is diagnosed your doctor may use stimulation testing to confirm the diagnosis, along with IGF-1 to monitor the effectiveness of GH replacement if it is being used as treatment. However, the best index of the effectiveness of GH treatment of children who are GH-deficient is observation of an increase in their hight velocity and their absolute height.  Repeat testing for growth hormone deficiency may occur as a child reaches adulthood to see if continued replacement is necessary.

    Stimulation testing is requested in adults when patients have symptoms of GHD. Suppression testing may be done when a pituitary tumour is suspected, and may be used along with IGF-1 levels and other hormone levels to monitor the effectiveness of treatment for these conditions. Monitoring may continue at regular intervals for many years to watch for recurrence.

    Since GH is released by the pituitary in bursts, random GH levels are not very useful. There is too much overlap between abnormal results and normal daily variation. GH levels will be higher first thing in the morning and will increase with exercise and stress.

  • What does the test result mean?

    GH suppression test:

    If your GH levels are not significantly suppressed during a GH suppression test (they stay higher than they should) and:

    • you have symptoms of gigantism or acromegaly
    • other pituitary hormone levels are normal and/or controlled
    • your IGF-1 levels are high

    it is likely that you are producing too much GH and it is causing complications. If you have other pituitary hormones that are abnormal, then you may have a condition causing hyperpituitarism. If a mass shows up on an X-ray, CT scan, or MRI ; then you may have a pituitary or very rarely another sort of tumour. If you are being monitored for a previous tumour, then you may be having a recurrence.

    GH stimulation test:

    If your GH levels are not significantly stimulated during a GH stimulation test (they stay lower than they should) and:

    • you have symptoms of GHD
    • other pituitary hormone levels are normal and/or controlled
    • your IGF-1 level is low

    then it is likely that you have a deficiency of GH that your doctor may treat. If your TSH level is low then that should be addressed first as thyroid deficiencies can cause symptoms similar to GHD. You may also have a more general decrease in pituitary function.

  • Is there anything else I should know?

    Pituitary tumours are the most common cause of excess GH production but such tumours may also cause deficiencies. Presence of a pituitary tumour can not only affect GH production, but may also affect production of other pituitary hormones, such as ACTH (Cushing’s syndrome) or  prolactin (galactorrhoea). If the tumour is relatively large it may inhibit all pituitary hormone production and cause damage to the surrounding tissues.

    Factors that can interfere with GH testing include:

    • Stress, exercise, and low blood glucose levels
    • Drugs that can increase GH include: amphetamines, arginine, dopamine, oestrogens, glucagon, histamine, insulin, levodopa, methyldopa, and nicotinic acid.
    • Drugs that can decrease GH levels: corticosteroids and phenothiazines.
    • Radioactive scan within a week of the test (with some laboratory methods)

    Abnormal GH levels can usually be modified once the causes are identified. Synthetic GH is available to alleviate deficiencies in children (treatment of adults with GHD is more controversial). Combinations of surgery, medication, and radiation can be used to treat pituitary tumours that are causing excess GH production. It is important to identify GH abnormalities as soon as possible to get a good outcome. If left untreated, the GH deficient child's short stature will remain. The bone growth changes associated with gigantism and acromegaly are permanent.

    There can be long-term complications from GH abnormalities. Acromegaly, for instance, can cause colonic polyps (increasing a patient’s risk of developing colon cancer), diabetes, high blood pressure, and visual abnormalities. If a pituitary tumour permanently damages pituitary cells then multiple hormone replacement may be necessary. Increased bone growth may also lead to trapped nerves (carpal tunnel syndrome), arthritis, and weak bones.

  • What conditions are treated with GH therapy?

    Besides GHD, children may be treated with growth hormone replacement if they have:

    • Chronic renal insufficiency
    • Prader-Willi syndrome
    • Turner's syndrome
    • Growth failure at 4 yrs or older and were born small for gestational age
    • Short stature homeobox-containing gene (SHOX) deficiency

    Treating children with GH replacement who are short but do not have GHD is controversial. This is also true of adults, whether or not they have documented GHD. The medicine has associated risks and side effects, is expensive, and there are not enough data to support its benefits.

  • Why would athletes be tested for GH?

    Because GH promotes muscle growth in adults it may be taken by some as a performance enhancing steroid. Athletes may be tested for GH when they are being tested for other performance enhancing drugs.

  • What other tests might be requested to evaluate my GH production?

    Although they are not routinely requested, other tests, such as insulin-like growth factor-1, binding protein-3 (IGFBP-3), and growth hormone releasing hormone (GHRH) are sometimes ordered to help evaluate GH production.