The Adrenal Enzyme Block Detector
17-OHP is a steroid precursor that accumulates when the adrenal enzyme 21-hydroxylase isn't working properly. Think of it as traffic piling up behind a roadblock—if the enzyme can't convert 17-OHP into cortisol, it backs up and gets shunted into androgen production instead. This is the hallmark of congenital adrenal hyperplasia (CAH).
What is 17-Hydroxyprogesterone (17-OHP)?
17-OHP is an intermediate in cortisol synthesis. 21-hydroxylase converts it to 11-deoxycortisol (cortisol pathway). Deficiency causes accumulation of 17-OHP which is shunted to androgen production. Draw AM in follicular phase. ACTH stimulation test confirms borderline cases.
↑ What High 17-Hydroxyprogesterone (17-OHP) Means
Congenital adrenal hyperplasia (21-hydroxylase deficiency)—the most common adrenal genetic disorder. Classic CAH presents at birth. Non-classic (late-onset) CAH presents in adolescence/adulthood with symptoms mimicking PCOS: hirsutism, acne, irregular periods.
Common symptoms:
Classic CAH neonates: ambiguous genitalia (females), salt-wasting crisis · Non-classic CAH: hirsutism, acne, irregular periods, infertility (mimics PCOS) · Children: precocious puberty, accelerated growth then short adult stature
↓ What Low 17-Hydroxyprogesterone (17-OHP) Means
Not clinically significant.
Common symptoms:
Not applicable
Why It Matters
When normal:
Screens for congenital adrenal hyperplasia (CAH)
Distinguishes late-onset CAH from PCOS
Part of newborn screening in most countries
Guides glucocorticoid replacement in CAH
Risks if abnormal:
Very high (>1500 ng/dL): classic CAH—salt-wasting crisis in neonates
Moderately high (200-1500): non-classic CAH
Untreated CAH: adrenal crisis, virilization, precocious puberty
What Can Cause Abnormal Levels?
21-Hydroxylase Deficiency (CAH)
80% likely95% of CAH cases. Autosomal recessive. Carrier frequency ~1:60. Classic (severe) or non-classic (mild).
Non-Classic CAH
50% likelyMild enzyme deficiency. Prevalence 1:100-1:1000. Presents like PCOS with hirsutism, acne, irregular periods.
PCOS (mildly elevated)
PCOS can mildly elevate 17-OHP. If >200 ng/dL baseline, do ACTH stimulation to rule out CAH.
Timing/Cycle Phase
Must draw in AM, follicular phase. Luteal phase and pregnancy naturally elevate 17-OHP.
What You Can Do
Draw AM, follicular phase (day 3-5 of cycle in women)
Impact: Correct timing prevents false positives \u00B7 Timeline: At testing
If baseline >200 ng/dL: ACTH stimulation test
Impact: Stimulated 17-OHP >1000 confirms non-classic CAH \u00B7 Timeline: One-time diagnostic
If lifestyle changes aren't enough:
Genetic testing for CYP21A2 mutations
Impact: Confirms diagnosis and guides genetic counseling \u00B7 Timeline: One-time
Recommended retest: One-time diagnostic; then per CAH monitoring if diagnosed
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