17-OH Progesterone (17-hydroxyprogesterone)
Reference values
| Population | Basal 17-OHP (nmol/L) | Interpretation |
|---|---|---|
| Newborn (screening days 2–5 on filter paper) | Variable alert threshold according to birth weight and gestational age + in general: > 30–50 nmol/L = positive screening requiring confirmation + premature infants and low-birth-weight newborns have physiologically higher 17-OHP values (placental steroidogenesis) → thresholds adjusted for weight | Positive screening → confirmation plasma serum assay + cortisol + DHEA-S + electrolytes + renin + aldosterone + CYP21A2 genotyping |
| Adult woman — follicular phase | 0.5–2.5 nmol/L (0.16–0.83 ng/mL) | Early follicular phase blood draw (Days 3-5) in the morning on an empty stomach + 17-OHP physiologically increases mid-cycle (LH surge) and during the luteal phase + increased values during pregnancy (placental contribution) |
| Adult woman — luteal phase | 1.0 to 10.0 nmol/L | Physiological augmentation + do not diagnose non-classic CAH based on luteal values or without cycle stage specification |
| Adult male | 0.5 to 3.0 nmol/L | Stable values (no cyclic variation) + slightly higher than the woman's follicular phase |
| Pre-pubescent child | 0.3 to 1.5 nmol/L | Low values before puberty |
Clinical forms of CAH due to 21-hydroxylase deficiency
| Shape | Residual enzyme activity | Clinical Presentation and 17-OHP |
|---|---|---|
| Virilizing classic form with salt wasting (most severe) | < 1 % residual 21-hydroxylase activity | Newborn: virilization of female external genitalia (sexual ambiguity in XX girls - clitoromegaly + labial fusion + urogenital sinus) + normal male genitalia in boys (but macroorchidism possible) + adrenal crisis at day 7-21 (vomiting + dehydration + hyponatremia + hyperkalemia + hypoglycemia + shock) if undiagnosed + very high 17-OHP (> 100 nmol/L) + low aldosterone + high renin |
| Simple virilizing classic form (salt-wasting) | 1–2 % residual activity | No adrenal crisis + virilization of female fetuses + in boys: precocious puberty + growth acceleration + bone age advancement + very high 17-OHP (> 30–100 nmol/L) |
| Non-classical form (late - HCS-NC) | 20–50 % residual activity | Adult and adolescent onset + symptoms of hyperandrogenism: hirsutism + severe acne + menstrual irregularities + oligomenorrhea + infertility + mild clitoromegaly + premature adrenarche in children + often confused with PCOS + moderately elevated basal 17-OHP (3–30 nmol/L) + confirmation by ACTH stimulation test (post-ACTH 17-OHP > 30 nmol/L = NC-HSC) |
ACTH stimulation test (Synacthen test)
- Indication Moderately elevated basal 17-OHP (3-30 nmol/L) + suspicion of non-classical CAH + workup for hirsutism + treatment-resistant PCOS-like symptoms + premature adrenarche + unexplained infertility
- Protocol: basal sample (T0) → IV or IM injection of tetracosactide (Synacthen® – synthetic ACTH analogue) 250 µg → sample at T+60 minutes → measurement of 17-OHP + cortisol + DHEA-S + androstenedione
- Interpretation : 17-OHP to T60 < 10 nmol/L = normal + 10–30 nmol/L = zone grise + hétérozygote possible → génotypage CYP21A2 + > 30 nmol/L = confirmed non-classical HCS + New nomogram (basal 17-OHP + stimulated 17-OHP) to distinguish carriers from affected individuals
Differential diagnosis of elevated 17-OHP
- Polycystic Ovary Syndrome (PCOS) 17-OHP baseline slightly elevated in 5–10 % of PCOS (ovarian origin of androgens) → normalization after ACTH stimulation (the response < 30 nmol/L (excluding HCS-NC) + high LH/FSH + PCOS on ultrasound
- Androgen-producing adrenal and ovarian tumors: 17-OHP can be elevated if there is a steroid-producing tumor + adrenal CT scan + ovarian ultrasound + very high DHEA-S if of adrenal origin
- 11β-hydroxylase deficiency (5 % of HCS): accumulation of 11-deoxycortisol and 11-deoxycorticosterone → virilization + hypertension (mineralocorticoid effects of 11-deoxycorticosterone) + normal or slightly elevated 17-OHP + 11-deoxycortisol assay
- Luteal phase or pregnancy: Physiologically elevated 17-OHP + always specify the moment of the cycle before interpreting + repeat in the follicular phase if in doubt
HCS Treatment
- Classical forms — hydrocortisone: Oral hydrocortisone 10–20 mg/m²/day in 3 doses (8 AM + 12 PM + 10 PM) → cortisol replacement + suppression of excessive ACTH secretion → reduction of 17-OHP and androgen production + doses adjusted for age + body surface area + 17-OHP and androstenedione (monitoring markers) + target: morning 17-OHP before hydrocortisone intake between 3–10 nmol/L + double or triple doses during intercurrent illnesses (sick day rule)
- Salt-wasting forms — fludrocortisone: fludrocortisone (Florinef®) 0.05–0.2 mg/day orally + oral NaCl in infants + replacement of deficient aldosterone → correction of hyponatremia + hyperkalemia + prevention of adrenal crises + renin target in the high-normal range
- Acute adrenal crisis — life-threatening emergency: hydrocortisone IV or IM 50–100 mg/m² bolus then continuous infusion 50–100 mg/m²/24 h + 0.9% NaCl % + IV glucose + correction of hyponatremia + hyperkalemia + hypoglycemia + continuous monitoring + parents of children with classic CAH must be trained in emergency intramuscular hydrocortisone injection at home (emergency kit)
- Non-classical forms: Treatment only if symptomatic + hirsutism: low-dose hydrocortisone +/- anti-androgens (spironolactone + cyproterone acetate) +/- oral contraceptives. Menstrual irregularities: hydrocortisone +/- oral contraceptives. Infertility: hydrocortisone to normalize ovulation + ovulation induction if necessary.
- Genital feminization surgery discussed in XX girls with severe virilization of external genitalia + controversial timing + multidisciplinary decision + indispensable psychological support
Call 911 or go to the ER immediately if a newborn from day 7 to day 21 presents with vomiting + lethargy + refusal to feed + dehydration + poor weight gain + especially if the newborn screening on the blood spot was positive for 17-OHP — these signs suggest an adrenal crisis of CAH with salt wasting, a life-threatening metabolic emergency within hours without treatment with IV hydrocortisone + saline. Never wait for biological test results to initiate treatment if clinical suspicion is high.
For the diagnosis and monitoring of non-classic HCS in adolescent and adult women, 17-OHP testing and ACTH stimulation testing if indicated, Clinique Omicron offers medical consultations at its service points in Quebec and through telemedicine. To make an appointment, visit cliniqueomicron.ca.
Consult at Clinique Omicron
Clinique Omicron's physicians and nurse practitioners (NPs) measure 17-OHP in the workup of hirsutism plus menstrual irregularities plus infertility or premature adrenarche, prescribe the ACTH stimulation test if basal 17-OHP is moderately elevated, refer to pediatric endocrinology for classic forms and to adult endocrinology or gynecology for non-classic forms, and monitor hydrocortisone treatment (17-OHP + androstenedione + growth + bone age in children). Consultations are available at several service points in Quebec and via telemedicine. To make an appointment, visit cliniqueomicron.ca.
The content of this page is for informational purposes only and does not substitute for medical advice from a physician or endocrinologist. The interpretation of 17-OH progesterone should always take into account the timing of the menstrual cycle, age, weight, and clinical context. The diagnosis and treatment of classic and non-classic CAH require specialized endocrinological follow-up.
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