17-Hydroxyprogesterone

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
Sample Required?
A blood sample drawn from a vein in your arm or blood from a heelstick for an infant.

How is it used?
The 17-hydroxyprogesterone (17-OHP) test is routinely ordered as part of newborn screening in the United States to detect congenital adrenal hyperplasia (CAH), a group of inherited disorders caused by specific gene mutations and associated with cortisol-related enzyme deficiencies. About 90% of CAH cases are caused by a mutation in the CYP21A2 gene that leads to a 21-hydroxylase deficiency and to accumulation of 17-OHP in the blood.

Up to 75% of newborns affected by 21- hydroxylase deficiency CAH will also produce less aldosterone, a hormone that regulates the retention of salt. The loss of too much fluid and salt in the urine can lead to a life-threatening adrenal crisis also called "salt-wasting" crises.

The 17-OHP test may be used to screen for CAH before symptoms appear or confirm a CAH diagnosis in persons with symptoms. The newborn screen is so sensitive that there may be a significant number of false positive test results. Positive 17-OHP screening tests may be repeated, or other tests performed, such as androstenedione and testosterone. If a 17-OHP test is abnormal, then an ACTH stimulation test may be also be ordered as a follow-up test. Molecular genetic testing may be performed to detect CYP21A2 gene mutations that can cause the condition. A karyotype test may be ordered as a follow-up test to detect chromosome disorders and to help determine a baby's sex. Electrolytes may be ordered to measure the person's sodium and potassium levels.

Measurement of 17-OHP in the blood may also be used to aid in the diagnosis of CAH in older children and adults who may have a milder, "late-onset" form.

If someone is diagnosed with 21-hydroxylase deficiency, treatment will involve suppressing ACTH production and replacement of the deficient cortisol with glucocorticoid treatment. A 17-OHP test may be used periodically to monitor the effectiveness of this treatment.

A 17-OHP test may also sometimes be used, along with other hormone tests, to help rule out CAH in people who have similar symptoms, such as hirsutism and irregular periods. This includes women with suspected polycystic ovarian syndrome (PCOS) and infertility, and rarely those with suspected adrenal or ovarian cancers.