17-Hydroxyprogesterone Test

A 17-hydroxyprogesterone test, often written as 17-OHP, measures a steroid the adrenal glands make as part of cortisol production. It is used mainly to screen for and monitor congenital adrenal hyperplasia, a group of inherited conditions that affect how the adrenal glands build their hormones.

What the test measures

17-Hydroxyprogesterone is an intermediate compound that the adrenal glands produce on the pathway toward making cortisol. Several enzymes are needed to carry that pathway through to completion. When one of those enzymes, most often 21-hydroxylase, does not work well, the pathway backs up and 17-OHP accumulates in the blood. Measuring it therefore offers a window into how smoothly adrenal steroid production is running.

Because 17-OHP sits at a branch point in steroid synthesis, a blockage further along can push the gland toward making more adrenal androgens. That connection is why this single measurement links to questions about congenital adrenal hyperplasia and to some causes of androgen excess in both children and adults.

Where 17-OHP fits in steroid production

Adrenal steroid synthesis is a stepwise process in which one molecule is converted into the next by a specific enzyme. 17-OHP is a recognizable waypoint along that route. When the step that follows it is impaired, the body cannot finish making cortisol efficiently, so the precursor pools and spills over into other steroid pathways. Understanding this branch point explains both why 17-OHP rises and why androgen-related signs can accompany the change.

Why a clinician might order it

17-OHP is a routine part of newborn screening programs in many places, helping detect congenital adrenal hyperplasia early. Beyond the newborn period, a clinician may order it when evaluating ambiguous genitalia, unusually early puberty, unexplained virilization, irregular periods, or difficulty conceiving, and to help distinguish congenital adrenal hyperplasia from other causes of androgen excess such as polycystic ovary syndrome. It is also used to follow people who already carry a diagnosis of congenital adrenal hyperplasia over time.

How the test generally works

17-OHP is measured from a blood sample drawn from a vein. In newborn screening it is usually obtained from a heel-prick blood spot collected in the first days of life. When a borderline value needs clarification, a clinician may arrange an ACTH stimulation test, in which 17-OHP is measured before and after a stimulating signal so the adrenal response can be assessed. The choice of method depends on age and the clinical question, and the laboratory assay used can influence the reported value.

How to prepare

17-OHP follows a daily rhythm and tends to be highest in the morning, so an early-morning draw is often preferred. In people who menstruate, timing within the cycle can matter, and a clinician may specify a particular day. Recent corticosteroid use and acute stress or illness can affect results. Sharing a current medication list and relevant history with the testing team helps the result be read correctly.

What can affect the result

Several factors shift 17-OHP independently of any inherited condition, which is why context is essential.

• Time of day: levels are generally higher in the morning, mirroring the daily cortisol rhythm.
• Menstrual cycle phase: values can differ across the cycle in people who menstruate.
• Stress and illness: acute physical stress can transiently raise the level.
• Medications: recent corticosteroid use can lower or alter the result.
• Age: newborns, especially those born early, are interpreted with separate age-specific cut-offs.

Classic and non-classic congenital adrenal hyperplasia

Congenital adrenal hyperplasia is not a single picture. The classic forms tend to appear early, sometimes detected through newborn screening, and are associated with more pronounced changes in adrenal hormone production. Non-classic, or later-onset, forms are generally milder and may not become apparent until adolescence or adulthood, when signs of androgen excess such as irregular periods or unwanted hair growth prompt evaluation. 17-OHP behaves differently across these forms, which is part of why a borderline value in an adult may need a stimulation test to clarify, while a markedly high value in a newborn carries different weight.

This range of presentations also explains why 17-OHP is interpreted so carefully. The same test serves both as an early screen and as a tool for sorting out androgen excess later in life, and the meaning of a given value depends heavily on the person's age and the question being asked. A clinician weighs the result against that context rather than against a single universal cut-off.

How results are generally interpreted

Interpretation depends on age, the time of day, and the clinical question, and is always made by a clinician in context.

• Clearly high 17-OHP raises suspicion for congenital adrenal hyperplasia, most often due to 21-hydroxylase deficiency, and usually prompts further confirmatory testing.
• Mildly elevated 17-OHP may reflect a milder, later-onset form or may be a transient finding, so it is commonly rechecked or assessed with a stimulation test.
• Normal 17-OHP makes classic congenital adrenal hyperplasia unlikely but is interpreted alongside the broader picture.

Illustrative reference ranges

The values below are illustrative only and vary substantially by laboratory, assay, age, sex, time of day, and menstrual cycle phase. Always use the range printed on your own report.

Related tests

17-OHP is often evaluated with other adrenal and reproductive hormones, and a borderline value may lead to a stimulation test for clarification. For related cortisol and androgen tests, see the blood tests index. Background on relevant disorders, including polycystic ovary syndrome and congenital adrenal hyperplasia, appears under conditions, while general steroid physiology is covered in the hormones index. The guides index offers help reading hormone reports.