The 17-hydroxyprogesterone (17-OHP) test is routinely ordered as part of newborn screening in the United States to detect congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency. CAH is 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 21-hydroxylase gene (also called P450c1 or CYP21A2) and may be detected due to the accumulation of 17-OHP in the blood.
The 17-OHP test may be used to screen for CAH in older children or adults before symptoms appear or to confirm a CAH diagnosis in people with symptoms.
17-OHP testing may produce false-positive test results. If the level is elevated but not so high that it is diagnostic of CAH, other tests may be performed, such as androstenedione and testosterone. An ACTH stimulation test may be also be ordered as a follow-up test (in CAH, ACTH stimulation will markedly increase 17-OHP levels). 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 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, a 17-OHP test may be used periodically to monitor the effectiveness of treatment.
Ruling out CAH
A 17-OHP test may also sometimes be used, along with other hormone tests, to help rule out CAH in women who have symptoms such as excess facial and body hair and irregular periods. This includes women with suspected polycystic ovarian syndrome (PCOS) and infertility, and rarely those with suspected adrenal or ovarian cancers.
Development of male secondary sex characteristics (virilization)
This test may sometimes be ordered in older children or in adults when the milder form of CAH (late-onset) is suspected. The 17-OHP test may also be conducted when a girl or woman is experiencing symptoms that may be due to CAH or may be due to another condition, such as PCOS. Symptoms may include:
If a newborn or infant has significantly elevated concentrations of 17-OHP, then it is likely that he or she has CAH. If a person has moderately increased levels, then that person may have a less severe case of CAH or may have an 11-beta-hydroxylase deficiency (another enzyme defect that is associated with CAH).
Normal 17-OHP results mean that it is likely that the person tested does not have CAH due to a 21-hydroxylase deficiency.
Low or decreasing concentrations in a person with CAH indicate a response to treatment. High or increasing levels may indicate that changes in treatment are required.
This article was last reviewed on September 17, 2013. | This article was last modified on May 7, 2014.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.