Unit Converter
Progesterone
(Key Female Reproductive Hormone - Critical in Ovulation, Luteal Function, Pregnancy & Fertility Evaluation)
Synonyms
- Progesterone
- P4
- Luteal hormone
- Ovarian progesterone
- Corpus luteum hormone
Units of Measurement
- pmol/L
- nmol/L
- ng/mL
- ng/dL
- ng/100 mL
- ng%
- ng/L
- µg/L
Molecular Weight
314.47 g/mol
Key Unit Conversions
ng/mL ↔ nmol/L
1 ng/mL=3.18 nmol/L1\ \text{ng/mL} = 3.18\ \text{nmol/L}1 ng/mL=3.18 nmol/L 1 nmol/L=0.314 ng/mL1\ \text{nmol/L} = 0.314\ \text{ng/mL}1 nmol/L=0.314 ng/mL
ng/dL ↔ ng/mL
1 ng/mL=100 ng/dL1\ \text{ng/mL} = 100\ \text{ng/dL}1 ng/mL=100 ng/dL
µg/L
1 µg/L=1 ng/mL1\ \text{µg/L} = 1\ \text{ng/mL}1 µg/L=1 ng/mL
pmol/L
1 nmol/L=1000 pmol/L1\ \text{nmol/L} = 1000\ \text{pmol/L}1 nmol/L=1000 pmol/L
ng%
\text{ng%} = \text{ng/dL}
Description
Progesterone is a steroid hormone produced mainly by:
- Corpus luteum in the ovary
- Placenta (after 8–10 weeks of pregnancy)
- Adrenal cortex (minor contribution)
- Testes (very small amount)
It is essential for:
- Ovulation confirmation
- Endometrial maturation
- Maintenance of early pregnancy
- Regulation of menstrual cycle
- Breast development
- Increasing basal body temperature after ovulation
Clinically, progesterone is a cornerstone marker in infertility workup, luteal phase assessment, early pregnancy evaluation, and diagnosis of ectopic pregnancy.
Physiological Role
- Prepares endometrium for implantation
- Maintains pregnancy until placental takeover
- Suppresses uterine contractions
- Modulates maternal immune response
- Promotes breast lobuloalveolar development
- Regulates hypothalamic GnRH & LH pulses
- Increases basal body temperature (0.3–0.5°C in luteal phase)
Clinical Significance
LOW Progesterone
1. Anovulation / Luteal Phase Deficiency
- Infertility
- Irregular cycles
- Recurrent implantation failure
- Assisted reproduction monitoring
2. Early Pregnancy Threat
Low progesterone associated with:
- Threatened miscarriage
- Ectopic pregnancy
- Poor placental support in early weeks
3. Ovarian insufficiency
- Premature ovarian failure
- Menopause
- Hypothalamic amenorrhea
4. Medications
Antiestrogens, some antiepileptics.
HIGH Progesterone
Physiological
- Normal luteal phase
- Pregnancy (very high)
- Following ovulation induction
- Luteal support therapy
Pathological
- Corpus luteum cyst
- Ovarian tumor (rare)
- Adrenal disorders (CAH)
- Congenital virilizing syndromes
Reference Intervals
Women (Non-Pregnant)
| Phase | Progesterone |
| Follicular phase | 0.2 – 1.4 ng/mL (0.6 – 4.5 nmol/L) |
| Ovulation | 0.8 – 3.0 ng/mL (2.5 – 9.5 nmol/L) |
| Luteal phase | 3 – 20 ng/mL (10 – 64 nmol/L) |
Ovulation confirmation:
>3 ng/mL suggests ovulation
>10 ng/mL indicates robust luteal function
Pregnancy
| Trimester | Progesterone |
| 1st | 10 – 44 ng/mL |
| 2nd | 19 – 82 ng/mL |
| 3rd | 65 – 290 ng/mL |
Men
- 0.1 – 1.0 ng/mL (0.3 – 3.2 nmol/L)
Postmenopausal
- <0.5 ng/mL
Diagnostic Uses
1. Ovulation Confirmation
Serum progesterone at:
- Day 21 of a 28-day cycle
- Or 7 days before expected menses
Interpretation:
- 3 ng/mL → ovulation likely
- <3 ng/mL → anovulation
2. Luteal Phase Assessment
- Infertility workup
- ART monitoring
- Luteal support therapy management
3. Early Pregnancy Evaluation
Low progesterone suggests:
- Threatened abortion
- Non-viable pregnancy
- Ectopic pregnancy
- Poor placental function
4. Pregnancy Viability Test
- P4 < 5 ng/mL → non-viable pregnancy (90% predictive)
- P4 > 20 ng/mL → viable intrauterine pregnancy likely
5. Ovarian Function Testing
- Polycystic ovary syndrome (PCOS)
- Menopause
- Ovarian insufficiency
6. Assessment in CAH
Mild elevation may assist in characterization.
Analytical Notes
- Serum preferred (stable levels)
- Timing critical for ovulation/luteal assessment
- Hemolysis minimal effect
- Assay interference possible with exogenous progesterone analogues
- Morning levels preferred in pregnancy evaluation
Clinical Pearls
- Progesterone spikes AFTER ovulation, so a mid-luteal level is most informative.
- Levels fluctuate hourly → always interpret with clinical context.
- Low progesterone does not alone diagnose miscarriage, but supports ultrasound findings.
- In IVF, progesterone supplementation greatly elevates serum levels — interpretation differs.
- Early pregnancy: P4 <10 ng/mL → high risk of adverse outcome.
Interesting Fact
The name “progesterone” comes from “pro-gestation”, highlighting its essential role in supporting and maintaining pregnancy.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Steroid Hormones
- Endocrine Society Clinical Practice Guidelines - Reproductive Hormones
- ACOG - Early Pregnancy & Luteal Assessment
- ASRM - Infertility Evaluation Guidelines
- Mayo Clinic Laboratories - Progesterone
- ARUP Consult - Reproductive Endocrinology
- NIH / MedlinePlus - Progesterone Test