Growth Hormone

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Also known as: GH; Human Growth Hormone (HGH); Somatotropin
Formal name: Growth Hormone
Related tests: IGF-1 (Insulin-like growth factor-1; also called Somatomedin C); GHRH (Growth Hormone Releasing Hormone); Glucose Tolerance Test; Cortisol; ACTH; TSH; Glucose; Prolactin

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.

The Test Sample

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.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

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.

The Test

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.