Progesterone
Corpus luteum hormone for cycle regulation, pregnancy, and GABA modulation
Also known as
Definition
Progesterone is a steroid hormone produced primarily in the corpus luteum (after ovulation) and in the placenta (during pregnancy). Small amounts are also produced in the adrenal glands and, in men, the testes. Progesterone prepares the uterus for implantation, maintains pregnancy, modulates GABA receptors (anxiolytic effect), influences sleep (via the allopregnanolone metabolite), and exerts anti-estrogenic effects on breast tissue.
| Parameter | Value |
|---|---|
| Unit | nmol/l (ng/ml) |
| Reference Range | Women: Follicular phase: < 3.2 nmol/l (< 1 ng/ml) | Luteal phase: 5.7–78 nmol/l (1.8–25 ng/ml) | Postmenopause: < 3.2 nmol/l | Men: 0.7–4.3 nmol/l (0.2–1.4 ng/ml) |
| Optimal Range (lab2go) | Women: Luteal phase > 32 nmol/l (> 10 ng/ml) (lab2go Optimum Zone — adequate luteal strength for cycle health) |
Conversion: 1 ng/ml = 3.18 nmol/l. US labs use ng/ml (luteal phase: 1.8–24 ng/ml).
↓ What a low value means
Low progesterone in the luteal phase (< 16 nmol/l / < 5 ng/ml) indicates luteal phase insufficiency, anovulatory cycles, corpus luteum dysfunction, or perimenopausal transition. Consequences: luteal phase defect, early pregnancy loss, estrogen dominance syndrome, sleep disturbances, anxiety tendency, PMS symptoms.
↑ What a high value means
Elevated progesterone outside the luteal phase or pregnancy may indicate a corpus luteum cyst, adrenal hyperplasia (11β-hydroxylase deficiency), or exogenous administration. During pregnancy, elevated progesterone is normal and essential.
✓ How to optimize this marker
Ensure adequate zinc (zinc-dependent steroid hormone synthesis). Vitamin B6 (cofactor for progesterone synthesis). Magnesium reduces PMS through progesterone modulation. Reduce stress (cortisol competes with progesterone for shared precursors — 'pregnenolone steal'). Regulate cycle through balanced body composition.
When to test
On day 7 after presumed ovulation (approximately cycle day 21 in a 28-day cycle) for luteal phase assessment. With fertility concerns, recurrent miscarriages, PMS, anovulatory cycles, or suspected luteal phase insufficiency. Always interpret in the context of cycle timing.
Frequently asked questions
What is the pregnenolone steal and does it affect my progesterone level? +
Pregnenolone is the shared precursor for cortisol, progesterone, and DHEA. Under chronic stress, the body prioritizes cortisol production from pregnenolone — potentially at the expense of progesterone. This 'steal' is biochemically plausible, but the clinical magnitude in humans is scientifically debated.
Why is the timing of progesterone measurement so important? +
Progesterone varies greatly across the cycle: < 1 ng/ml in the follicular phase, 1.8–25 ng/ml in the luteal phase. A measurement without cycle data is barely interpretable. The ideal time is day 7 after ovulation (approximately cycle day 21), the point of the luteal phase peak.
Does bioidentical progesterone work better than synthetic progestins? +
Bioidentical progesterone (micronized progesterone, chemically identical to endogenous P4) has a more favorable side effect profile than synthetic progestins. It acts anxiolytically, promotes sleep (via allopregnanolone), and carries no increased cardiovascular risk. The WHI study used synthetic progestin — not bioidentical progesterone.
How is progesterone connected to sleep? +
Progesterone is metabolized in the brain to allopregnanolone, which acts as a positive allosteric modulator at the GABA-A receptor — producing calming, sleep-promoting effects. This explains the sleep-enhancing effect of progesterone in the second half of the cycle and why menopausal women with low progesterone frequently experience sleep disturbances.
Sources
- Prior JC (2020) Progesterone for Symptomatic Perimenopause Treatment. Facts Views Vis Obgyn.
- Stanczyk FZ et al. (2013) Progestogens used in postmenopausal hormone therapy. Endocr Rev.
- Monteleone P et al. (2018) Symptoms of menopause — global prevalence, physiology and implications. Nat Rev Endocrinol.
Last Reviewed: May 28, 2026 · sina
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.