17-OH Progesterone
Also known as: 17-OHP, 17-Hydroxyprogesterone
What Does 17-OH Progesterone Measure?
17-OH Progesterone (17-OHP) is a steroid hormone produced primarily by the adrenal glands and, to a lesser extent, by the ovaries and testes. It is an intermediate compound in the biosynthesis of cortisol and androgens, sitting at a critical junction in the steroidogenesis pathway. A blood test measuring 17-OHP quantifies the concentration of this hormone in the bloodstream, typically reported in nanograms per deciliter (ng/dL) or nanomoles per liter (nmol/L). The test is usually performed in the morning when hormone levels are at their peak due to the natural circadian rhythm of adrenal secretion.
Why Does 17-OH Progesterone Matter?
17-OHP is most clinically significant as the primary diagnostic marker for Congenital Adrenal Hyperplasia (CAH), particularly the form caused by 21-hydroxylase deficiency, which accounts for over 90% of CAH cases. When the enzyme 21-hydroxylase is deficient or absent, 17-OHP cannot be properly converted to cortisol, causing it to accumulate to abnormally high levels. This buildup redirects the steroidogenesis pathway toward androgen production, leading to symptoms such as virilization, ambiguous genitalia in newborns, early puberty, and adrenal crises. Beyond CAH, elevated 17-OHP can signal other adrenal disorders, polycystic ovary syndrome (PCOS), or adrenal tumors, making it a valuable tool in evaluating unexplained androgen excess in women and children.
Normal Ranges
Males
Adult males: 27–199 ng/dL (0.8–6.0 nmol/L); levels are higher in the morning and decline throughout the day
Females
Follicular phase: 15–70 ng/dL; Luteal phase: 35–290 ng/dL; Postmenopausal: <51 ng/dL; values fluctuate with the menstrual cycle
Children
Varies significantly by age and sex: Newborns (after 24–48 hrs): <400 ng/dL; Prepubertal children: <100 ng/dL; Pubertal children: approach adult ranges. Newborn screening uses different cutoffs based on gestational age and birth weight.
Causes of High Levels
- Congenital Adrenal Hyperplasia (CAH) due to 21-hydroxylase deficiency — the most common cause, where a genetic enzyme defect blocks cortisol synthesis causing 17-OHP accumulation
- 11-beta-hydroxylase deficiency — another form of CAH where a different enzyme block leads to 17-OHP buildup along with hypertension
- Adrenal tumors or carcinomas — cancerous or benign adrenal growths that produce excess steroid hormones including 17-OHP
- Polycystic Ovary Syndrome (PCOS) — ovarian dysfunction can cause mildly to moderately elevated 17-OHP, particularly in the luteal phase
- Stress or acute illness — physical stress activates the adrenal glands, transiently raising 17-OHP and other adrenal hormones
- Non-classic CAH (late-onset CAH) — a milder, partial enzyme deficiency presenting in adolescence or adulthood with elevated basal or stimulated 17-OHP levels
Causes of Low Levels
- Adrenal insufficiency (Addison's disease) — destruction or dysfunction of the adrenal cortex reduces production of all adrenal steroid precursors including 17-OHP
How to Improve Your 17-OH Progesterone
Diet
- Maintain a balanced, low-glycemic diet rich in whole grains, legumes, and vegetables to support stable blood sugar and reduce cortisol demand on the adrenal glands
- Include healthy fats such as avocados, olive oil, and fatty fish, as cholesterol is the essential precursor for all steroid hormone synthesis
- Reduce intake of processed foods, refined sugars, and trans fats, which promote systemic inflammation and can dysregulate adrenal hormone production
- Ensure adequate protein intake (0.8–1.2g per kg body weight) to provide amino acid building blocks for enzyme production and overall hormone regulation
- Consume foods rich in B vitamins (leafy greens, whole grains, eggs) which support adrenal enzyme function and cortisol metabolism
Supplements
- Vitamin C (500–1000 mg/day) — the adrenal glands have the highest concentration of vitamin C in the body; supplementation may support healthy adrenal function and cortisol synthesis
- Magnesium glycinate (200–400 mg/day) — supports HPA axis regulation and may help reduce excessive adrenal stimulation
- Adaptogenic herbs such as Ashwagandha (300–600 mg/day of standardized KSM-66 extract) — shown in clinical studies to modulate cortisol and support adrenal balance, which may indirectly normalize 17-OHP
Related Biomarkers
Frequently Asked Questions
What is the ACTH stimulation test and why is it used with 17-OHP?
The ACTH stimulation test (also called the cosyntropin stimulation test) involves injecting a synthetic form of ACTH hormone to maximally stimulate the adrenal glands, then measuring 17-OHP levels 30–60 minutes later. This test is used when baseline 17-OHP levels are borderline or mildly elevated, particularly to diagnose non-classic (late-onset) Congenital Adrenal Hyperplasia. In individuals with partial 21-hydroxylase deficiency, the stimulated 17-OHP will rise excessively (typically above 1500 ng/dL), even if the baseline level was only mildly elevated. This test helps distinguish true enzyme deficiency from other causes of mild 17-OHP elevation.
Is 17-OH Progesterone tested in newborn screening?
Yes, 17-OHP is a standard component of newborn screening programs in many countries, including all 50 U.S. states, as part of heel-prick blood spot testing performed within the first 24–48 hours of life. Early detection of elevated 17-OHP is critical for identifying the classic salt-wasting form of CAH, which can cause life-threatening adrenal crisis within the first weeks of life if untreated. It is important to note that premature infants often have physiologically elevated 17-OHP due to immature adrenal function, which can lead to false-positive results. Confirmatory testing is always required before a diagnosis is made.
Can 17-OH Progesterone levels fluctuate in women?
Yes, significantly. In women with regular menstrual cycles, 17-OHP levels follow a predictable pattern: they are lower during the follicular phase (the first half of the cycle) and rise substantially during the luteal phase (after ovulation), sometimes doubling or tripling. This is because the corpus luteum — the structure that forms after ovulation — produces 17-OHP. For accurate diagnostic interpretation, women should ideally have their 17-OHP tested during the early follicular phase (days 1–5 of the menstrual cycle). Levels also rise during pregnancy. Failure to account for cycle timing can lead to misinterpretation of results.