At a glance
Also known as
17-OHP; 17-OH progesterone; Progesterone - 17-OH
Why get tested?
To detect and monitor treatment for congenital adrenal hyperplasia (CAH); sometimes to help rule out other conditions with similar symptoms.
When to get tested?
When an infant's sex is not obvious (ambiguous genitalia), when a young female has or other symptoms of , 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?
None, but an early morning collection may be requested; it may also be requested that the blood sample be collected at a specific time durig a woman's menstrual cycle. The test should not be ordered if the patient is taking steroids.
What is being tested?
17-OHP is steroid hormone produced by the adrenal gland as part of the process of making the important hormone cortisol. Several 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 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 , the development of male sexual characteristics, in both females and young males.
These inherited enzyme deficiencies and the resulting excess 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. About 90% of CAH cases are caused by a mutation in the 21-hydroxylase gene ( also called CYP-21 or P450c1 or CYP21A2) and may be detected due to the accumulation of 17-OHP in the blood. The disease is caused when both genes,, one from each parent, have mutations that decrease or stop the activity of the enzyme for which the gene codes. Parents may be carriers, and carriers may not have any signs of the disease.
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 , 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.