When should the blood sample be drawn for 17-OHP testing?

The sample should be drawn in the morning, ideally before 9 a.m., because 17-OHP follows a diurnal rhythm that peaks in the early morning. In menstruating females, follicular-phase testing is preferred to avoid luteal-phase elevations.

What does an elevated 17-OH progesterone indicate?

Markedly elevated basal values suggest classic 21-hydroxylase-deficient CAH. Moderate elevations may indicate non-classic CAH, carrier status, luteal-phase physiology, or rarely an adrenal or ovarian tumour; ACTH stimulation testing clarifies borderline results.

Can 17-OHP be elevated in conditions other than CAH?

Yes. Physiological luteal-phase rise, polycystic ovary syndrome, premature or stressed neonates, and some steroid-secreting tumours can all raise 17-OHP, so interpretation requires clinical context and often dynamic testing or genetic confirmation.

Is fasting required for the 17-OH progesterone test?

No, fasting is not required for 17-OHP, though morning timing is important to capture the peak of the diurnal rhythm.

How is 17-OHP used to monitor treatment in CAH?

Serial measurements guide glucocorticoid dosing. The goal is to suppress 17-OHP into the upper-normal to moderately elevated range without over-treating; very high values indicate under-replacement, and undetectable levels suggest glucocorticoid excess.

What is the role of ACTH stimulation testing with 17-OHP?

When basal 17-OHP is borderline, cosyntropin stimulation unmasks partial 21-hydroxylase deficiency by provoking an exaggerated rise in 17-OHP, distinguishing non-classic CAH and carriers from unaffected individuals.

Does the assay method affect 17-OHP results?

Yes. Immunoassays can show cross-reactivity with other steroids and may overestimate 17-OHP. Liquid chromatography–tandem mass spectrometry is more specific and is the preferred confirmatory method when results are equivocal.

How long do 17-OH progesterone results take?

Results are typically available within 2–3 business days from specimen receipt at the LabCorp laboratory. Reflex or send-out testing for LC-MS/MS confirmation may extend turnaround.

BML-HRF-016female hormonesUSA

17-OH Progesterone

The 17-OH Progesterone test measures a steroid intermediate that accumulates in 21-hydroxylase deficiency, serving as the primary biochemical marker for congenital adrenal hyperplasia. It is used to screen newborns and investigate androgen excess in children and adults, with basal values interpreted by age, sex, menstrual phase, and time of day; borderline results require ACTH stimulation testing.

Biomarkers

Blood (serum)

Sample

2–3 business days

Turnaround

Fasting

What is the 17-OHP test?

The 17-OH Progesterone test measures a steroid precursor that accumulates when the enzyme 21-hydroxylase is deficient, making it the primary biochemical marker for congenital adrenal hyperplasia due to 21-hydroxylase deficiency. Practitioners order it to screen infants with ambiguous genitalia or salt-wasting crises, to investigate children with premature adrenarche or accelerated growth, and to diagnose non-classic CAH in adolescents and adults presenting with hirsutism, oligomenorrhoea, or infertility. Beyond newborn screening, 17-OHP serves as a gatekeeper test: a clearly elevated basal morning value supports the diagnosis, while borderline results prompt a cosyntropin stimulation test to unmask partial enzyme deficiency. In patients with established CAH, serial 17-OHP measurements guide glucocorticoid dosing, though interpretation must account for the time since the last hydrocortisone dose and the known diurnal rhythm. The test is less useful for adrenal insufficiency or other steroidogenic defects where cortisol and ACTH are the primary markers.

What does the 17-OHP test measure?

17-OHP(17-Hydroxyprogesterone)

Range: Follicular phase <200 ng/dL, luteal phase <285 ng/dL, postmenopausal <51 ng/dL; prepubertal children <100 ng/dL. Values are sex-, age-, menstrual phase-, and assay-dependent.Optimal: In the context of CAH screening, unstimulated morning 17-OHP below 200 ng/dL in the follicular phase is reassuring; values above 1,000 ng/dL are highly suggestive of classic CAH, and intermediate results warrant dynamic testing. Optimal therapeutic targets in treated CAH patients are debated but generally aim for concentrations in the high-normal to two- to threefold-elevated range to balance androgen suppression against glucocorticoid excess.ng/dL / nmol/L

17-Hydroxyprogesterone is a C21 steroid intermediate in the adrenal and gonadal biosynthesis of cortisol and sex hormones. It is formed when 17α-hydroxylase acts on progesterone in the zona fasciculata of the adrenal cortex and the ovaries. The enzyme 21-hydroxylase then converts 17-OHP to 11-deoxycortisol in the cortisol pathway. Because 21-hydroxylase deficiency is the most common cause of congenital adrenal hyperplasia, 17-OHP accumulates and becomes a sensitive screening and diagnostic marker for that disorder. Smaller quantities are produced by the corpus luteum during the luteal phase, so physiological concentrations fluctuate across the menstrual cycle and rise during pregnancy.

Measurement of 17-OHP is the cornerstone of screening and diagnosis for 21-hydroxylase-deficient congenital adrenal hyperplasia, both in newborns and in children or adults with suspected non-classic forms. Marked basal elevations confirm classic CAH, while borderline or moderately raised values often require ACTH stimulation testing to distinguish heterozygotes and non-classic cases from unaffected individuals. The test is also used to monitor replacement therapy in known CAH, where the goal is to suppress 17-OHP into the upper-normal range without overtreatment.

Why is the 17-OHP test ordered?

Newborns with ambiguous genitalia, salt-wasting crisis, or positive newborn screening results suggestive of congenital adrenal hyperplasia
Children with signs of androgen excess — premature pubarche, advanced bone age, accelerated linear growth, or virilisation
Adolescent and adult females with hirsutism, severe acne, oligomenorrhoea, or anovulatory infertility when polycystic ovary syndrome work-up does not fully explain the phenotype
Evaluation of suspected non-classic CAH in individuals with a family history of the disorder or consanguinity
Monitoring of glucocorticoid replacement therapy in patients with known 21-hydroxylase-deficient CAH
Second-tier or reflex testing when newborn screening 17-OHP is elevated but equivocal, particularly in premature or stressed neonates
Pre-conception or antenatal carrier screening in at-risk populations or when a partner is a known carrier

Sample collection and turnaround

Sample type

Blood (serum)

Fasting required

Collection method

Venipuncture at patient service centre

Turnaround

2–3 business days

Collection notes

Phlebotomy at a LabCorp draw site. For CAH screening, collect in the morning (before 9 a.m. when feasible) to capture the peak of the diurnal rhythm. In menstruating females, note cycle day; follicular-phase sampling is preferred. In patients on glucocorticoid therapy, document the time of the last dose. Standard serum separator tubes are acceptable.

Specimen requirements

Minimum 0.5 mL serum. Separate from cells and refrigerate or freeze if analysis is delayed. Note the assay platform (immunoassay versus LC-MS/MS) for borderline results, as LC-MS/MS offers superior specificity.

What can affect 17-OHP results?

variableTime of day and diurnal rhythm

17-OHP follows the cortisol circadian rhythm, peaking in the early morning and reaching its nadir in the evening; samples for CAH screening should be drawn in the morning to maximise sensitivity.

elevatesMenstrual cycle phase

Luteal-phase progesterone production raises 17-OHP physiologically, so timing relative to menses must be recorded; testing is ideally performed in the follicular phase.

elevatesPrematurity and stress in neonates

Premature infants and sick newborns have immature adrenal enzyme activity and can show transiently elevated 17-OHP, leading to false-positive screening results that require careful clinical and biochemical follow-up.

elevatesCross-reactivity in immunoassays

Direct immunoassays can show cross-reactivity with other steroids, particularly 17-hydroxypregnenolone; liquid chromatography–tandem mass spectrometry eliminates this interference and is the preferred method when results are equivocal.

reducesGlucocorticoid therapy

Exogenous glucocorticoid suppresses ACTH and lowers 17-OHP; in treated CAH patients the timing of the sample relative to the last hydrocortisone dose affects interpretation.

elevatesOvarian or adrenal tumours

Rare steroid-secreting neoplasms can produce 17-OHP and other intermediates, mimicking or complicating the biochemical picture of CAH.

What do 17-OHP results mean?

Elevated

Markedly elevated basal 17-OHP (typically >1,000–1,500 ng/dL) strongly suggests classic 21-hydroxylase-deficient CAH. Moderate elevations (200–1,000 ng/dL) are seen in non-classic CAH, heterozygote carriers, luteal-phase physiology, ovarian hyperandrogenism, and some adrenal tumours; cosyntropin stimulation clarifies these. In treated CAH patients, persistently high values indicate under-replacement, while very low or undetectable concentrations suggest over-treatment with excess glucocorticoid.

Normal

A normal basal 17-OHP in a morning follicular-phase sample makes classic CAH unlikely but does not exclude non-classic CAH or heterozygote status; if clinical suspicion persists, proceed to ACTH stimulation testing. In treated CAH, a value in the upper-normal to moderately elevated range typically reflects adequate replacement.

Reduced

Low or undetectable 17-OHP is not clinically significant in most contexts and may be seen in patients on high-dose glucocorticoid therapy or with primary adrenal insufficiency due to causes other than 21-hydroxylase deficiency, where cortisol and ACTH are the relevant markers.

Note: Interpretation requires knowledge of age, sex, menstrual phase, time of day, and assay method. Borderline results often necessitate dynamic testing with cosyntropin; genetic confirmation by CYP21A2 sequencing is definitive. Serial monitoring in treated CAH should be timed consistently relative to medication dosing, and clinicians should not rely on a single value in isolation.

Frequently asked questions

17-Hydroxyprogesterone is a steroid precursor in cortisol synthesis. It accumulates when the enzyme 21-hydroxylase is deficient, making it the key marker for diagnosing congenital adrenal hyperplasia due to that enzyme defect.

How to access the 17-OHP test

The 17-OHP reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.

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About this page

Published: October 7, 2026

Last reviewed: October 7, 2026

References:

Speiser PW, et al. Congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. (2018)
New MI, et al. Nonclassical congenital adrenal hyperplasia. Endocr Rev. (2019)
Carmina E, et al. Non-classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency revisited: an update with a special focus on adolescent and adult women. Hum Reprod Update. (2017)
National Institute for Health and Care Excellence (NICE). Congenital adrenal hyperplasia guideline. (2021)

This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.

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