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) |
Agree on your personal target range with your doctor.
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 can point to cycles without ovulation (anovulatory cycles), reduced corpus luteum function, or the perimenopausal transition. A single measurement does not, however, establish the quality of the luteal phase: progesterone is released in pulses and fluctuates widely, and according to the American Society for Reproductive Medicine (ASRM) there is no reliable standard for diagnosing luteal phase deficiency. Links with sleep disturbances, anxiety, or PMS symptoms are discussed; a diagnosis does not follow from the value alone. Your doctor interprets the result.
↑ 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.
✓ What can influence this value
The progesterone level is determined mainly by the course of the cycle: it rises markedly after ovulation, falls after menopause, and is elevated in pregnancy. Further influences are body composition, the supply of micronutrients involved in steroid hormone synthesis such as zinc and vitamin B6, and stress. That cortisol and progesterone share precursors is biochemically correct; that stress lowers the progesterone level through this route (the so-called pregnenolone steal) has not been demonstrated. The timing of the blood draw within the cycle determines how informative the value is. The assessment is made by the treating doctor.
When to test
Progesterone is usually measured on day 7 after presumed ovulation (approximately cycle day 21 in a 28-day cycle); a rise in the luteal phase is taken as a sign that ovulation has occurred. A single measurement does not establish the quality of the luteal phase (ASRM). Occasions include fertility concerns, recurrent miscarriages, PMS, anovulatory cycles, or suspected luteal phase insufficiency. The value is always interpreted in the context of cycle timing.
Frequently asked questions
What is the pregnenolone steal and does it affect my progesterone level? +
Pregnenolone is a shared precursor of cortisol, progesterone, and DHEA. The term pregnenolone steal describes the assumption that under chronic stress the body preferentially converts pregnenolone to cortisol and therefore makes less progesterone. This mechanism has not been demonstrated in humans: cortisol is made in the adrenal glands, while progesterone in the second half of the cycle comes mainly from the corpus luteum. A low progesterone value is therefore no proof of such an effect.
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. It is usually measured on day 7 after ovulation (approximately cycle day 21), the point of the luteal phase peak; a rise is taken as a sign of ovulation. A single measurement does not establish the quality of the luteal phase, because progesterone is released in pulses (ASRM).
What distinguishes bioidentical progesterone from synthetic progestins? +
Bioidentical progesterone (micronized progesterone) is chemically identical to the body's own progesterone (P4); synthetic progestins are not. Progesterone taken from outside the body can raise the measured value. Your doctor decides whether any hormone therapy is appropriate, and which.
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.
Progesterone
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 updated: May 28, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.