Age-related declines in testosterone and HGH are associated with increased adiposity and decreases in lean mass and bone mineral density.
HGH Test
To help diagnose growth hormone (GH) deficiency or, less commonly, growth hormone excess; to evaluate pituitary function; to monitor the effectiveness of treatment for excess GH
When a child has slow growth, short stature, and delayed motor development or sometimes when an adult has decreased bone density and/or muscle strength and elevated blood lipid levels that could be related to growth hormone deficiency; when a child or adult has signs and symptoms suggestive of growth hormone excess, which can cause two rare conditions, gigantism, and acromegaly, respectively; when a pituitary disorder is suspected and other pituitary hormone levels are abnormal
Sample Required?
Usually, several blood samples, are drawn at timed intervals from veins; sometimes a single sample of blood, is drawn following a fast and rest, after a period of strenuous exercise, or after drinking a glucose (sugar) solution
Test Preparation Needed?
Follow any instructions you are given, such as to fast, in order to prepare for this test.
What is being tested?
Growth hormone (GH) is a hormone that is essential for normal growth and development in children. It promotes proper linear bone growth from birth through puberty. In both children and adults, growth hormone helps regulate the rate at which the body both produces energy from food (metabolism) and makes lipids, proteins, and glucose (sugar). It also helps regulate the production of red blood cells and muscle mass.
Growth hormone is produced by the pituitary gland, a small gland located at the base of the brain behind the bridge of the nose. It is normally released into the blood in pulses throughout the day and night with peaks that occur mostly during the night. Because of this, a single measurement of the level of GH in the blood is difficult to interpret and not usually clinically useful. The value will be higher if the sample is taken during a pulse and lower if it is taken during a period between pulses.
Therefore, procedures called growth hormone stimulation and suppression tests are most often used to diagnose conditions caused by a growth hormone deficiency or excess. These procedures are used in conjunction with signs and symptoms and growth factor levels (i.e., insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-binding protein 3).
GH deficiency
Some children have GH deficiency at birth (congenital), but some may develop a deficiency later due, for example, to a brain injury or tumor. These conditions can affect the pituitary gland, causing a decrease in pituitary function, resulting in a lowered production of pituitary hormones (hypopituitarism). Sometimes, the cause of the deficiency is not known, a category referred to as “idiopathic.”
In adults, growth hormone plays a role in regulating bone density, muscle mass, and glucose and lipid metabolism. It can also affect heart and kidney function. Deficiencies may begin in childhood or develop in adulthood. A deficiency can develop, for example, because of damage to the pituitary gland caused by a head injury, brain tumor, or surgery or radiation treatment. This can result in a decrease in pituitary hormones (hypopituitarism).
GH excess
Excess GH is most often due to a pituitary tumor (usually benign) that produces GH.
Too much GH in children can cause their long bones to continue to grow beyond puberty, resulting in the extremely rare condition, gigantism, with heights of 7 feet or more. Those with excess GH may also have thickening of facial features, general weakness, delayed puberty, and headaches. Pituitary tumors releasing excess growth hormone can cause loss of vision if they grow very large.
Excess GH in adults can lead to the rare condition, 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 levels can lead to enlarged hands and feet, enlarged facial bones, carpal tunnel syndrome, and abnormally enlarged internal organs. Excess GH can also cause skin tags and intestinal polyps.
Frequently, the pituitary tumor causing the excess can be surgically removed and/or treated with drugs or radiation. In most cases, this will cause GH and IGF-1 levels to return to normal or near-normal levels.
If left untreated, both acromegaly and gigantism can lead to complications such as type 2 diabetes, increased risk of cardiovascular disease, high blood pressure, arthritis, and in general, a decreased lifespan.
How is the sample collected for testing?
Growth hormone is released in pulses, so a single measurement of the blood level is not normally clinically useful. Therefore, growth hormone levels are usually measured using growth hormone suppression or stimulation procedures. After fasting for 10 to 12 hours, a blood sample is drawn from a vein in the arm. Then, under medical supervision, the suppression or stimulation procedure is performed. This may involve the use of an intravenous (IV) infusion. Blood samples are then drawn from a vein (or from the IV) at timed intervals.
Sometimes, a single sample of blood is drawn following a fast rest or after a period of strenuous exercise.
Is any test preparation needed to ensure the quality of the sample?
Follow any instructions you are given. In most cases, you should be fasting. Resting or strenuous exercise for a time period before collection may be required.
Children and pre-teens who are being tested for GH deficiency should be prepared for treatment with sex steroids for a few days prior to testing. Such treatment reduces the number of falsely low GH responses to stimulation. The health practitioner who is ordering the GH testing should provide the child’s parents with a prescription for such medications. Some healthcare practitioners will also prescribe propranolol prior to testing to reduce the number of falsely low GH responses to stimulation.
Testosterone Test
Testosterone tests are performed to determine the amount of testosterone in a sample of blood.
Testosterone is the hormone responsible for controlling fertility and the development of sperm in men or anyone with a penis. Testosterone also plays an important part in the development of male sex characteristics such as a deeper voice and certain patterns of muscle development and hair growth. In women or anyone with ovaries, testosterone impacts overall growth as well as the development of muscle and reproductive tissue.
Testosterone tests can be used to help diagnose health conditions in children and adults. Doctors also use testosterone tests to monitor hormone levels in patients who are receiving testosterone replacement therapy and transgender men who are on hormone therapy.
Purpose of the test
The purpose of testosterone testing is to evaluate the amount of testosterone in the blood. Testosterone levels that are outside of a normal range can cause changes to health and physical appearance. Measuring testosterone can be helpful in diagnosing medical conditions or monitoring a patient’s response to therapy:
Diagnosis: Doctors may check testosterone levels to determine the cause of a person’s symptoms. Testing can help identify testosterone deficiency or an elevated level of testosterone. Testosterone tests may be part of assessing patients with health conditions that can affect hormone levels.
Monitoring: Monitoring is how doctors follow a patient’s health over time. In people who have had abnormal testosterone tests in the past, follow-up testing may be used to track their testosterone levels.
Testosterone tests can also be used to monitor the health of transgender men. Transgender men are people who were assigned female at birth but identify as male. Some transgender men may choose to take hormone therapy to change their physical appearance to match their gender identity. Doctors may monitor testosterone levels in this group of men to ensure testosterone levels are maintained at a certain level.
What does the test measure?
A testosterone test measures the level of the hormone testosterone in the blood.
In men or anyone with a penis, testosterone is produced by the testicles and the adrenal gland, and it controls the development of sperm and male sex characteristics. In women or anyone with ovaries, testosterone is produced by the ovaries, the adrenal gland, and other tissues, and it aids in overall growth and development.
Testosterone in the blood can be either bound or free:
- Bound testosterone is attached to proteins such as albumin or sex hormone-binding globulin (SHBG). Most testosterone is bound to SHBG.
- Free testosterone, the active form, is all the remaining testosterone that is not bound to other substances.
- A total testosterone test measures both bound and free testosterone in a sample of blood. This is the most common type of testosterone test, and levels are commonly reported in nanograms per deciliter of blood (ng/dL). Less often, a test may be performed for free testosterone, which is reported in picograms per deciliter of blood (pg/dL).
Another less common test is for bioavailable testosterone, which is testosterone that can be used more readily by the body. Bioavailable testosterone includes all testosterone that is not bound to SHBG, including free testosterone and albumin-bound testosterone. Bioavailable testosterone is also commonly reported in nanograms per deciliter of blood (ng/dL).
When should I get a testosterone test?
Your doctor may order a testosterone test if you are experiencing symptoms that suggest hormone levels outside of a normal range.
In men or anyone with a penis, a testosterone test may be performed if you have symptoms that suggest a low testosterone level, such as:
- early or late onset of puberty;
- erectile dysfunction;
- fertility problems;
- osteoporosis or thinning of the bones;
- decrease in sex drive.
Doctors may also evaluate your testosterone levels even if you don’t have symptoms if you have a health condition that can affect hormone levels. For example, testosterone testing may be performed if you have HIV/AIDS, unexplained bone density loss, infertility, or anemia. If you have undergone certain types of cancer treatment such as chemotherapy or radiation to the testicles, you may also have your testosterone levels checked.
Doctors may check testosterone levels as part of a diagnostic work-up in women or anyone with ovaries if physical changes suggest a higher than normal level of testosterone. Changes may include the following:
- irregular periods;
- loss of periods;
- changes in hair growth patterns;
- voice changes;
- skin changes such as oily skin or acne;
- enlarged clitoris.
You may also have testosterone testing if you are a transgender man on masculinizing hormone therapy that is intended to induce and maintain male sex characteristics. Testing is recommended every three months during the first year of therapy as your dose is adjusted. After that, your doctor may suggest monitoring your testosterone levels one to two times per year.
If you have questions about testosterone testing, talk with your health care provider who can discuss whether this testing is appropriate in your situation.
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