Unit Converter
17-Hydroxyprogesterone
Synonyms
- 17-OHP
- 17-OH Progesterone
- 17α-Hydroxyprogesterone (17α-OHP)
- Hydroxyprogesterone (OHP)
- 17 Alphahydroxyprogesterone
- 17α-hydroxypregn-4-ene-3,20-dio
Units of Measurement
- nmol/L
- ng/mL
- ng/dL
- ng/100mL
- ng%
- ng/L
- µg/L
Synonyms
- 17-OHP
- 17-Hydroxyprogesterone
- 17-α-Hydroxyprogesterone
- 17-OH-Progesterone
- OHPG (older abbreviation)
Units of Measurement
ng/dL, ng/mL, µg/L, nmol/L, pmol/L
(Varies by assay and country)
Description
17-Hydroxyprogesterone (17-OHP) is a steroid hormone produced in the adrenal cortex and gonads. It is a key intermediate in the synthesis of:
- Cortisol
- Androgens
- Progesterone pathway hormones
It becomes clinically relevant because elevated levels indicate impaired cortisol synthesis, most commonly in 21-Hydroxylase Deficiency (21-OHD) -the leading cause of Congenital Adrenal Hyperplasia (CAH).
Physiological Role
1) Intermediate in Steroidogenesis
Pathway:
Cholesterol → Pregnenolone → 17-OHP → 11-Deoxycortisol → Cortisol
2) Adrenal & Gonadal Secretion
Adrenal cortex (zona fasciculata + zona reticularis) is the major producer.
Gonads contribute mildly, especially in luteal phase.
3) ACTH-Dependent Regulation
High ACTH → high 17-OHP
Low ACTH → low 17-OHP
Hence, CAH patients show very high 17-OHP due to compensatory ACTH stimulation.
Clinical Significance
A) Elevated 17-OHP
Most important causes:
- Congenital Adrenal Hyperplasia (CAH)
- Classic (salt-wasting or simple virilizing)
- Non-classic CAH (late-onset)
- Classic (salt-wasting or simple virilizing)
- Adrenal tumors
- PCOS (mild elevation)
- Preterm infants (physiological elevation)
B) Low 17-OHP
- Steroidogenic defects upstream
- Adrenal insufficiency
- Exogenous glucocorticoid therapy
Reference Intervals
| Group | Reference Range |
| Adults – Male | < 220 ng/dL (SI: < 6.67 nmol/L) |
| Female – Follicular | < 80 ng/dL (SI: < 2.42 nmol/L) |
| Female – Luteal | < 285 ng/dL (SI: < 8.64 nmol/L) |
| Female – Postmenopausal | < 51 ng/dL (SI: < 1.55 nmol/L) |
| Newborn (first 24–72 h) | 100–1000 ng/dL* (varies widely; crucial for CAH screening) |
| Preterm infants | Significantly higher (immature adrenal cortex) |
*Newborn ranges vary by birth weight and day of sampling -interpret with caution.
(Tietz 8E + ESAP 2024 endocrine table confirms these ranges.)
17-OHP in Newborn Screening
Why newborn values are high?
Adrenal immaturity + stress of delivery → physiologic elevation.
Hence:
- Term infant: lower baseline
- Preterm infant: higher values → higher false positives
- Low-birth-weight infants: require corrected ranges
Modern screening uses:
- Fluoroimmunoassay (first-tier)
- LC–MS/MS (second-tier) for accuracy
Clinical Use Cases
1) Diagnosis of CAH (21-Hydroxylase Deficiency)
Basal levels:
- > 2,000 ng/dL → classic CAH
- 200–800 ng/dL → possible non-classic CAH → ACTH stimulation test needed
- < 200 ng/dL → usually normal
2) ACTH Stimulation Test
After cosyntropin (250 µg) injection:
- Peak > 1,000 ng/dL strongly suggests CAH
- Used particularly in:
- Ambiguous genitalia
- Hirsutism
- PCOS vs non-classic CAH
- Adrenal tumors
- Ambiguous genitalia
3) Monitoring CAH therapy
Glucocorticoids suppress 17-OHP levels.
Targets vary by center but typically:
- Avoid very high peaks (undertreatment)
- Avoid very low values (overtreatment, Cushingoid risks)
Units Description & Conversions
Unit Meanings
| Unit | Meaning |
| ng/dL | nanogram per deciliter |
| ng/mL | nanogram per milliliter |
| µg/L | microgram per liter |
| nmol/L | nanomole per liter |
Molecular weight of 17-OHP ≈ 330.45 g/mol
Clinical Pearls
- Early-morning sampling is ideal due to ACTH circadian rhythm.
- Luteal phase 17-OHP is naturally higher -avoid misclassification.
- Preterm infants can show extremely high 17-OHP without CAH.
- In PCOS, levels are mildly elevated; CAH shows distinctly higher values.
- LC–MS/MS is preferred for exact measurement -minimizes false positives.
Interesting Medical Fact
17-OHP became a universal newborn screening marker after the 1977 discovery that CAH caused dangerously low cortisol and salt-wasting crises in newborns - early detection has since saved thousands of lives.
References
Primary
- Tietz Clinical Chemistry and Molecular Diagnostics, 8th Edition -Steroid hormones section.
- ESAP 2024 -Endocrine reference intervals (17-OHP table).
Secondary
- Mayo Clinic Laboratories - 17-OHP pediatric & adult reference ranges.
- ARUP Consult -Congenital Adrenal Hyperplasia testing.
- NIH / NLM -Steroidogenesis pathways.
- Turcu AF et al. “Nonclassic CAH: Diagnosis and Management.” Endocr Rev.
- Speiser PW. “Congenital adrenal hyperplasia.” N Engl J Med.