17-OHP

17-Hydroxyprogesterone

Hormones

What is 17-Hydroxyprogesterone?

17-Hydroxyprogesterone (17-OHP) is a steroid hormone intermediate in the cortisol biosynthesis pathway. It is produced in the adrenal cortex and gonads from progesterone by the enzyme 17α-hydroxylase and is subsequently converted to 11-deoxycortisol by 21-hydroxylase (CYP21A2) on the pathway to cortisol production. 17-OHP is the primary biochemical marker for congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency—the most common inborn error of steroid metabolism, occurring in approximately 1 in 15,000 live births worldwide.

When 21-hydroxylase is deficient, 17-OHP accumulates because it cannot be efficiently converted to cortisol. The resulting cortisol deficiency drives increased ACTH secretion (attempting to stimulate cortisol production), which further stimulates the adrenal cortex and shunts steroid precursors—including 17-OHP—toward androgen synthesis. This explains the hallmarks of CAH: cortisol deficiency, aldosterone deficiency (in severe salt-wasting forms), and androgen excess. 17-OHP follows a circadian rhythm similar to cortisol, with highest levels in the early morning, and varies with menstrual cycle phase (highest in the luteal phase).

Why It Matters

17-OHP is the definitive screening and diagnostic marker for 21-hydroxylase deficiency CAH. Newborn screening programs worldwide measure 17-OHP in dried blood spots to identify classic CAH before life-threatening salt-wasting crises occur—this has dramatically reduced infant mortality from CAH. In older children and adults, 17-OHP measurement (baseline and ACTH-stimulated) diagnoses non-classic (late-onset) CAH, which is far more common (1 in 100–1,000 depending on ethnicity) and presents with hyperandrogenic symptoms resembling PCOS. Distinguishing non-classic CAH from PCOS is clinically important because management and genetic counseling differ.

Normal Reference Ranges

GroupRangeUnit
Baseline (Follicular Phase, Women)15–70ng/dL
Baseline (Luteal Phase, Women)35–290ng/dL
Adult Men33–190ng/dL
ACTH-Stimulated (Non-classic CAH cutoff)>1,000ng/dL
Newborns (>37 weeks, day 2–3)<400ng/dL

Reference ranges may vary by laboratory. Always compare results to the ranges provided by your testing facility.

What High 17-OHP Levels Mean

Common Causes

  • Classic congenital adrenal hyperplasia (21-hydroxylase deficiency)—markedly elevated
  • Non-classic (late-onset) congenital adrenal hyperplasia—moderately elevated
  • Normal luteal phase of menstrual cycle
  • Premature birth (transiently elevated in preterm neonates)
  • Adrenal tumors (occasionally)
  • Ovarian tumors (rarely)
  • PCOS (mildly elevated in some patients)

Possible Symptoms

  • Ambiguous genitalia in 46,XX newborns (classic CAH)
  • Salt-wasting crisis in neonates (vomiting, dehydration, hyponatremia, hyperkalemia)
  • Premature adrenarche and accelerated growth in children
  • Hirsutism, acne, and menstrual irregularity in women (non-classic CAH)
  • Male-pattern baldness in women
  • Infertility
  • Advanced bone age and compromised final adult height

What to do: A baseline early morning follicular-phase 17-OHP >200 ng/dL is suspicious for non-classic CAH and warrants ACTH stimulation testing: 250 µg cosyntropin is administered IV, and 17-OHP is measured at 0 and 60 minutes. A stimulated 17-OHP >1,000 ng/dL is diagnostic of 21-hydroxylase deficiency. In classic CAH, baseline 17-OHP is typically >1,000–10,000 ng/dL. Confirmatory CYP21A2 genotyping is recommended for genetic counseling and to determine carrier status in partners. Treatment of classic CAH requires lifelong glucocorticoid replacement (hydrocortisone in children, prednisolone or dexamethasone in adults), with mineralocorticoid replacement (fludrocortisone) for salt-wasting forms. Non-classic CAH is treated only if symptomatic—options include low-dose glucocorticoids, oral contraceptives, or anti-androgens.

What Low 17-OHP Levels Mean

Common Causes

  • Normal finding in most individuals
  • 17α-hydroxylase deficiency (rare form of CAH—opposite enzyme defect)
  • Adrenal suppression from exogenous glucocorticoids
  • Hypopituitarism

Possible Symptoms

  • Low 17-OHP is rarely clinically significant in isolation
  • In 17α-hydroxylase deficiency: hypertension, hypokalemia, absent puberty (due to inability to produce sex steroids)
  • Ambiguous genitalia in 46,XY individuals (17α-hydroxylase deficiency)

What to do: Low 17-OHP is normal and does not require treatment. If 17α-hydroxylase deficiency is suspected (hypertension with hypokalemia, sexual infantilism, elevated deoxycorticosterone and corticosterone), specialized steroid profiling and genetic testing of CYP17A1 confirm the diagnosis. Treatment includes sex steroid replacement for pubertal development, glucocorticoid replacement to suppress ACTH and correct the mineralocorticoid excess, and potassium management. This is an extremely rare condition compared to 21-hydroxylase deficiency.

When Is 17-OHP Testing Recommended?

  • As part of newborn screening programs (dried blood spot)
  • When evaluating hyperandrogenism in women to rule out non-classic CAH
  • When ambiguous genitalia is present in a newborn
  • When a child shows signs of premature adrenarche or accelerated growth

Frequently Asked Questions

Classic CAH is severe 21-hydroxylase deficiency (enzyme activity <2%) presenting at birth. It has two subtypes: salt-wasting (most severe, with both cortisol and aldosterone deficiency) and simple virilizing (cortisol deficiency with intact aldosterone). Classic CAH causes ambiguous genitalia in affected females and salt-wasting crises in both sexes if untreated. Non-classic (late-onset) CAH is a milder deficiency (enzyme activity 20–50%) that does not cause genital ambiguity or salt wasting but manifests later in childhood or adulthood with premature adrenarche, hirsutism, acne, menstrual irregularity, and infertility. Non-classic CAH is far more common—affecting 1 in 100–1,000 individuals depending on ethnicity (highest in Ashkenazi Jewish, Hispanic, and Mediterranean populations). Many carriers are completely asymptomatic.
Newborn screening for CAH using 17-OHP has a high false-positive rate, particularly in premature and low-birth-weight infants. Premature neonates have physiologically elevated 17-OHP because their adrenal cortex is still maturing, and hepatic conjugation of steroid precursors is incomplete. Stress of illness, sepsis, and critical care can also elevate 17-OHP. The false-positive rate for CAH screening is estimated at 0.5–1%, compared to a true-positive rate of about 1 in 15,000. This means for every true CAH case detected, approximately 50–100 infants have false-positive screens requiring follow-up. Second-tier testing with liquid chromatography-tandem mass spectrometry (LC-MS/MS) and measurement of steroid ratios significantly reduces false positives compared to immunoassay alone.
Non-classic CAH and PCOS can present almost identically—both cause hirsutism, acne, menstrual irregularity, and elevated androgens in women of reproductive age. Distinguishing them matters because non-classic CAH is a genetic condition requiring different management and genetic counseling. Key differences: baseline morning follicular-phase 17-OHP is elevated (>200 ng/dL) in non-classic CAH and typically normal in PCOS. ACTH stimulation with 17-OHP measurement is the definitive test: a stimulated 17-OHP >1,000 ng/dL confirms 21-hydroxylase deficiency. CYP21A2 genotyping provides definitive confirmation. In PCOS, LH/FSH ratio may be elevated and AMH is often high—these are typically normal in non-classic CAH. Approximately 1–5% of women evaluated for hyperandrogenism who would otherwise be diagnosed with PCOS actually have non-classic CAH.

Related Biomarkers

CortisolCortisolACTHAdrenocorticotropic HormoneDHEA-SDHEA-SulfateTTestosteroneP4Progesterone

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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Reference ranges may vary between laboratories. Always consult your healthcare provider for interpretation of your specific test results.

Disclaimer: SymptomGPT is not a medical diagnosis tool and does not provide medical advice. Always consult a qualified healthcare professional. If you are experiencing a medical emergency, call 911 immediately.