At a Glance
Why Get Tested?
To detect and monitor treatment for congenital adrenal hyperplasia (CAH); sometimes to help rule out other conditions.
When to Get Tested?
When an infant has ambiguous genitalia, when a young female has hirsutism or other symptoms of virilisation, when a male child has premature sexual development, and periodically to monitor CAH treatment.
A blood sample drawn from a vein in your arm or blood from a heelprick for an infant.
Test Preparation Needed?
The Test Sample
What is being tested?
This test measures the amount of the hormone 17-hydroxyprogesterone (17-OHP) in the blood. 17-OHP is produced by the adrenal gland as part of the process of making the important hormone cortisol. Several enzymes are required for this process. If a person is born with either not enough of one of these enzymes or an abnormal form of an enzyme, their adrenal gland cannot produce cortisol efficiently. Depending on which enzyme is abnormal, another important hormone, aldosterone may also be affected. In such cases, 17-OHP builds up. Some of the excess 17-OHP is used up by making male hormones (androgens). Excess androgens can cause virilisation, the development of male sexual characteristics, in both females and young males.
These inherited enzyme deficiencies and the resulting excess androgens occur in a group of disorders called congenital adrenal hyperplasia (CAH). Most cases of CAH are caused by a lack of the enzyme 21-hydroxylase. In more severe forms of CAH, the condition becomes evident in infancy or childhood, while milder forms, known as late-onset or non-classical CAH, may not become evident until later in life, including adulthood. In the more serious form of CAH, excess androgens can cause female babies to be born with ambiguous genitalia, meaning it can be difficult to tell at birth if they are male or female. In less severe forms in females the first sign of the condition may be hirsutism, irregular menstruation or infertility. Males with this condition may start to develop sexual characteristics prematurely in early childhood (precocious puberty) or experience infertility as adults.
In many people with CAH the adrenal gland cannot produce enough of another hormone, aldosterone. Aldosterone prevents the body from losing too much sodium salt and water in the urine. Babies with CAH who have aldosterone deficiency can suffer from life-threatening "salt-wasting" crises and may have low blood sodium levels (hyponatraemia) and high blood potassium levels (hyperkalaemia).
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm or by pricking the heel of an infant.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed, but the doctor may request an early morning collection. The doctor may also request that blood be collected at a specific time during a woman's menstrual cycle.
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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.