Serum 17-hydroxyprogesterone (17-OHP) is an adrenal and ovarian steroid used to evaluate congenital adrenal hyperplasia (CAH), adrenal tumors, and disorders of steroidogenesis. Values vary by menstrual cycle phase and increase significantly during pregnancy.
| Units | Menstruating Female | 1st Trimester | 2nd Trimester | 3rd Trimester | |
|---|---|---|---|---|---|
| ng/dL | 20–100 | Follicular | 172–941 | 172–941 | 512–2772 |
| 100–250 | Mid-cycle peak | ||||
| 100–500 | Luteal | ||||
| nmol/L | 0.6–3 | Follicular | 5.2–28.5 | 5.2–28.5 | 15.5–84 |
| 3–7.5 | Mid-cycle peak | ||||
| 3–15 | Luteal | ||||
Causes of High 17-Hydroxyprogesterone
- Congenital adrenal hyperplasia (21-hydroxylase deficiency) — most common
- Nonclassic (late-onset) CAH
- Adrenal adenoma or carcinoma
- Ovarian steroid-producing tumors
- PCOS
- Stress, critical illness
- Glucocorticoid resistance
- Hyperprolactinemia (mild elevation)
- Pregnancy (placental changes in late gestation)
- CYP21A2 carrier state (borderline levels)
Causes of Low 17-Hydroxyprogesterone
- Adrenal insufficiency (primary or secondary)
- Hypopituitarism with low ACTH
- Over-treatment with glucocorticoids in CAH
- Severe illness suppressing adrenal output
- Early follicular phase baseline
- Very early pregnancy (before placental steroidogenesis rises)