What this test measures
17-Hydroxyprogesterone (17-OHP) is a steroid hormone produced by the adrenal glands and, to a lesser extent, the ovaries and testes. It is an intermediate step in the pathway that makes cortisol and androgens. When the enzyme 21-hydroxylase is deficient — the most common form of Congenital Adrenal Hyperplasia — cortisol production is blocked, ACTH rises, and 17-OHP accumulates upstream of the block.
The test quantifies 17-OHP in serum. Because adrenal hormones follow a diurnal rhythm and because levels rise in the luteal phase in women, the sample should be drawn early morning (7–9 am) and, for cycling women, in the early follicular phase (day 2–5 of menses).
Why it matters
In India, classic CAH is detected in newborns through heel-prick screening in many tertiary centres, but milder "non-classic" CAH often presents in adolescence or adulthood with hirsutism, acne, irregular periods, or unexplained infertility — mimicking PCOS. A morning baseline 17-OHP > 2 ng/mL warrants an ACTH stimulation test; > 10 ng/mL is essentially diagnostic of 21-hydroxylase deficiency.
17-OHP is also monitored to titrate glucocorticoid therapy in known CAH patients, where the goal is suppression of adrenal androgen overproduction without over-treatment with steroids.
How to prepare
Sample is drawn early morning (between 7 and 9 am) when adrenal output peaks. In menstruating women, schedule for the early follicular phase (cycle day 2–5) — luteal-phase progesterone metabolism can falsely raise 17-OHP. Continue regular medications unless your doctor instructs otherwise. If on hydrocortisone or dexamethasone for known CAH, ask your endocrinologist about timing the dose relative to the draw.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| 17-Hydroxyprogesterone (ng/mL)[1][2] | Adult male: < 2.0 · Female follicular: < 0.8 · Female luteal: < 2.85 · Children > 1 yr: < 1.1 · Newborn (term): variable, lab-specific | Low or undetectable 17-OHP in a known CAH patient on steroid therapy suggests over-replacement. In an untreated patient, low values rule out 21-hydroxylase deficiency. | Morning baseline > 2 ng/mL is suspicious for non-classic CAH and should trigger an ACTH stimulation test. > 10 ng/mL is consistent with classic CAH or a strong non-classic presentation. Mildly raised levels can also be seen in PCOS, adrenal or ovarian tumours, and the luteal phase of a normal cycle. |
17-OH Progesterone — how to interpret a morning baseline
| 17-OHP (ng/mL) | Interpretation | Next step |
|---|---|---|
| < 2 | Normal | CAH essentially ruled out; consider other causes of hyperandrogenism (PCOS) |
| 2 – 10 | Equivocal | ACTH (cosyntropin) stimulation test to confirm or rule out non-classic CAH |
| > 10 | Likely CAH | Diagnostic of 21-hydroxylase deficiency (classic or severe non-classic); endocrine referral |
| > 100 (newborn) | Classic CAH | Urgent — risk of salt-wasting crisis; start glucocorticoid + mineralocorticoid |
Frequently asked questions
Why does the sample have to be taken in the morning?
Adrenal hormones follow a strong diurnal rhythm — they peak around 6–8 am and fall through the day. A late-afternoon sample can be falsely low and miss mild CAH.
I have PCOS — why is my doctor checking 17-OHP?
Non-classic Congenital Adrenal Hyperplasia is one of the most common conditions that mimics PCOS — same picture of irregular periods, acne and unwanted hair. A morning 17-OHP rules it out (or in) in a single blood test, and the treatment is different.
Should I be tested during a specific part of my cycle?
Yes — the early follicular phase (day 2 to day 5 of your period) is best. Progesterone rises in the luteal phase and can falsely raise the 17-OHP reading.
What if my baseline is borderline?
A morning baseline of 2–10 ng/mL is equivocal. The standard next step is an ACTH (cosyntropin) stimulation test: 17-OHP is measured before and 60 minutes after a synthetic ACTH injection. A stimulated value > 10 ng/mL is diagnostic of non-classic CAH.
Is 17-OHP tested in newborns in India?
Yes, many tertiary hospitals and private newborn-screening programmes include 17-OHP on the heel-prick panel because classic CAH can cause a life-threatening salt-wasting crisis in the first weeks of life. Universal coverage is still patchy across India.
I am on hydrocortisone for CAH — how often is 17-OHP checked?
Usually every 3 to 6 months during dose titration, then annually once stable. The aim is to suppress androgen excess without over-treating — most endocrinologists target a "slightly raised" 17-OHP rather than complete suppression.
Can stress raise 17-OHP?
Acute physical stress (severe illness, surgery) raises ACTH and therefore 17-OHP. Routine emotional stress does not change the result meaningfully.
Related Hormones / Endocrine tests
Tests commonly ordered alongside 17 OH PROGESTERONE, or that help interpret an unexpected result.
Sources & references
- Endocrine Society — Congenital Adrenal Hyperplasia Guideline · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — 17-Hydroxyprogesterone Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — 17 Hydroxyprogesterone · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Laboratories — 17-OH Progesterone · accessed 2026-05-30T00:00:00.000Z
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