At a Glance
Why Get Tested?
To screen for, detect, and monitor treatment for congenital adrenal hyperplasia (CAH); sometimes to help rule out other conditions
When to Get Tested?
As part of a routine newborn screen, when an infant has ambiguous genitalia, when a young female has hirsutism or other symptoms of virilization, 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 heelstick for an infant
Test Preparation Needed?
The Test Sample
What is being tested?
This test measures the amount of 17-hydroxyprogesterone (17-OHP) in the blood. 17-OHP is a precursor to cortisol; it is a substance used by the body to make cortisol. Cortisol is a hormone produced by the adrenal glands that helps break down protein, glucose, and lipids, maintains blood pressure, and regulates the immune system. The production of cortisol is stimulated by adrenocorticotropic hormone (ACTH), a hormone produced by the pituitary gland. Concentrations of cortisol normally vary throughout the day, peaking around 8 am and declining in the evening. Levels are increased with illness and stress.
Several enzymes are required to complete the production of cortisol. If one or more of the enzymes is deficient or dysfunctional, then inadequate amounts of cortisol are produced and cortisol precursors, such as 17-OHP, accumulate in the blood. The adrenal glands use up some of the excess 17-OHP by producing more androgens. Excess androgens can cause virilization, the development of male sexual characteristics, in both males and females. These inherited enzyme deficiencies and the resulting excess androgens lead to a group of disorders called congenital adrenal hyperplasia (CAH). The most common cause of CAH is a lack of the enzyme 21-hydroxylase, accounting for about 90% of cases. CAH is inherited as either a severe or mild type.
In the more serious form of CAH, severe 21-hydroxylase deficiencies and the influence of excess androgens can cause female babies to be born with ambiguous genitalia, making it difficult to initially determine if they are male or female. Males with this condition will appear normal at birth but start to develop sexual characteristics prematurely in early childhood. Females may develop hirsutism during childhood and adolescence, have irregular menstruation, and have other signs of virilization. Up to 75% of males and females affected by 21- hydroxylase deficiency CAH will also produce less aldosterone, an adrenal hormone that regulates the retention of salt. This can lead to life-threatening "salt-wasting" crises in male and female newborns in which too much fluid and salt are lost in the urine. Those affected may have low blood sodium levels (hyponatremia), high blood potassium levels (hyperkalemia), decreased aldosterone, and increased plasma renin activity. This severe, though less common form is most often detected in infancy during routine newborn screening or during early childhood.
In the milder, yet more common form of this disorder, there may be only partial deficiency of the enzyme. This type, sometimes called late-onset or non-classical CAH, can have symptoms that begin to appear any time during childhood, adolescence, or adulthood. The symptoms can be vague, may develop slowly over time, and may vary from person to person. Though this form of CAH is not life-threatening, it may cause problems with growth, development, and puberty in children and may lead to infertility in adults.
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.
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?
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.
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