What is a 17-hydroxyprogesterone (17-OHP) test?
This test measures the amount of 17-hydroxyprogesterone (17-OHP) in a sample of your blood. 17-OHP is a substance that your adrenal glands make.
Your adrenal glands are two small organs that sit on top of each kidney. They make different types of hormones you need to stay alive and healthy. Hormones are chemical messengers in your bloodstream that control the actions of certain cells or organs.
Normally, your adrenal glands use 17-OHP to make a hormone called cortisol. Cortisol helps control your energy levels, blood glucose (sugar), blood pressure, and your body's response to stress, illness and injury.
A 17-OHP test helps diagnose a group of uncommon, inherited genetic disorders that affect how well your adrenal glands make cortisol. These genetic adrenal gland disorders are called congenital adrenal hyperplasia (CAH).
People with CAH have a change in a gene that causes the lack of an enzyme that your adrenal glands need to make hormones. The most common type of CAH is caused by a lack of an enzyme called 21-hydroxylase. 21-hydroxylase helps your adrenal glands use 17-OHP to make cortisol.
Without enough 21-hydroxylase, the adrenal glands struggle to make enough cortisol. As the adrenal glands work harder to do their job, they become enlarged and make abnormally high levels of 17-OHP. These high levels of 17-OHP are a sign of CAH with 21-hydroxylase deficiency.
The adrenal glands use the extra 17-OHP to make larger than normal amounts of male sex hormones. This happens in children and adults of both sexes. So, tests for male hormones, including testosterone, are often used with 17-OHP tests to help diagnose CAH.
The symptoms of CAH depend on how much cortisol the adrenal glands are able to make. CAH is often organized into two groups based on how severe the symptoms are:
Classic CAH includes the most severe forms of the disorder. It's usually diagnosed at birth. Without diagnosis and treatment, severe CAH can be life-threatening. Serious symptoms may show up shortly after birth. They may include:
Newborn girls with severe CAH may have external genitals that are not clearly female or male. This is caused by high levels of male hormones. In newborn boys, the genitals usually appear normal, but sometimes the penis may be larger than usual.
Classic CAH that is caused by a 21-hydroxylase deficiency can be diagnosed with 17-OHP testing. Less often, CAH is caused by a lack of a different enzyme.
Nonclassic CAH includes mild forms of the disorder. It's also called late-onset CAH because symptoms show up between early childhood and early adulthood. It is almost always caused by a lack of 21-hydroxylase and can be found with a 17-OHP test.
Treatment is only needed if a person has symptoms. The symptoms depend on the person's age and sex. For example:
Other names: 17-OH progesterone, 17-OHP, 17 alphahydroxyprogesterone, 17 hydroxy progesterone: serum, progesterone: 17-hydroxy
What is it used for?
A 17-OHP test is used to help find and monitor the most common type of CAH, which is sometimes called 21-hydroxylase deficiency. The test is used to:
- Check all newborns for severe CAH (classic CAH). Newborn screening tests can't check for mild CAH (nonclassic).
- Help diagnose mild CAH in children, teens, and adults who have symptoms that could be caused by the disorder.
- Find out if treatment for CAH is working.
- Help rule out CAH in women who have certain symptoms such as large amounts of facial hair and irregular menstrual periods. These symptoms can also be caused by other conditions, such as polycystic ovarian syndrome (PCOS).
Why do I need a 17-OHP test?
Babies need a 17-OHP test as part of routine newborn screening tests to check for severe CAH:
- If you give birth in a hospital , your baby will usually have a 17-OHP test before going home. The test is most accurate when it's done more than 24 hours after birth. If your baby is tested sooner, ask your child's provider if a second test should be done at a later time. Some states require two tests for all babies.
- If you give birth at home, make sure your baby has all the necessary screening tests.
Symptoms of severe CAH usually begin within days or weeks after birth, but in certain cases, they may not show up until early childhood. These symptoms may be serious and include:
- Lack of energy
- Vomiting and other feeding problems
- Failure to thrive (not gaining weight and growing as expected)
Children, teens, and adults may need testing if they develop symptoms of mild CAH (nonclassic CAH):
In children and teens, symptoms of mild CAH may include:
- Rapid growth that stops at a younger age than usual. As a result, older teens and adults with CAH may be shorter than average.
- Signs of early puberty.
- Severe acne, which may continue into adulthood.
In girls and women, symptoms of mild CAH may include:
- More facial and/or body hair than usual
- Irregular menstrual periods or no periods at all
- Thinning hair on the head, especially near the temples (male pattern baldness)
- Enlarged clitoris
In boys and men, symptoms of mild CAH may include:
- Enlarged penis with small testicles (testes)
- Low sperm count
What happens during a 17-OHP test?
For a newborn screening, a health care professional will clean your baby's heel with alcohol. Then the provider will stick the baby's heel with a small needle to collect a few drops of blood. The heel will then be bandaged.
For older children and adults, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Will I need to do anything to prepare for the test?
There are no special preparations needed for a 17-OHP test.
Are there any risks to the test?
There is very little risk from a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly. Your baby may feel a little pinch when the heel is poked. A small bruise may form on the heel, but it should go away quickly.
What do the results mean?
The results of a 17-OHP test help show whether you or your child have the most common type of CAH, which is caused by a lack of 21-hydroxylase.
If test results show a normal amount of 17-OHP, it means that you or your child probably do not have CAH with 21-hydroxylase deficiency. If you or your child has symptoms, the provider may order other tests to figure out the cause.
If test results show higher than normal levels of 17-OHP, you or your child probably has CAH. The provider may order other tests to learn more about how CAH is affecting you or your child.
If you or your child is being treated for CAH, decreasing levels of 17-OHP over time means that the treatment is working. Treatment for CAH may include medicines to replace the cortisol your body can't make. Other medicines may also be needed, depending on the type of CAH. If a girl is born with atypical external genitals, surgery may also be done.
If you, your child, or another family member has been diagnosed with CAH, you may want to talk with a genetic counselor. Genetic counselors are trained in genetics and genetic testing. They can help you learn how likely you are to pass CAH to future children.
If you have questions about the results of a 17-OHP test, talk with your provider.
Learn more about laboratory tests, reference ranges, and understanding results.
Is there anything else I need to know about a 17-OHP test?
If the results of your 17-OHP test aren't clear, your provider may order another test to measure your 17-OHP. This is called an ACTH stimulation test. It involves measuring your cortisol and 17-OHP levels before and after you have an injection (shot) of ACTH (adrenocorticotropic hormone).
ACTH is a hormone your body makes to trigger your adrenal glands to make cortisol. If you have CAH, the ACTH injection will make your 17-OHP levels increase a lot, but it will not increase your cortisol levels.
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