Unit Converter
Estradiol (E2)
(Primary Estrogen – Marker for Ovarian Function, Fertility, Menopause & Hormonal Disorders)
Synonyms
- Estradiol
- 17β-Estradiol
- E2
- Estrogen hormone
- Ovarian estrogen
- Follicular estrogen
Units of Measurement
- pmol/L
- pg/mL
- pg/dL
- pg/100 mL
- pg%
- pg/L
- ng/L
1 pg/mL = 3.671 pmol/L
1 pg/mL = 100 pg/dL
1 pg/mL = 1000 pg/L
pg/dL = pg% = pg/100 mL
Description
Estradiol (E2) is the most biologically potent estrogen in humans.
It is produced mainly by the ovaries, with minor contributions from:
- Adrenal glands
- Testes
- Peripheral conversion of androgens (fat tissue)
E2 regulates:
- Menstrual cycle
- Ovulation
- Secondary sexual characteristics
- Bone metabolism
- Cardiovascular function
- Mood and cognition
Estradiol is essential in assessing:
- Fertility
- Puberty
- Menopause
- Polycystic ovary syndrome (PCOS)
- Hypogonadism
- Tumor-related hormonal changes
Physiological Role
Major functions include:
- Follicular growth
- Endometrial proliferation
- Bone density maintenance
- Lipid metabolism
- Vaginal & breast tissue development
- Feedback regulation of GnRH, LH, and FSH
Clinical Significance
Low Estradiol Levels
Seen in:
1. Menopause / Premature Ovarian Failure
- Hot flashes
- Vaginal dryness
- Osteoporosis risk
2. Hypogonadism
- Turner syndrome
- Hypothalamic amenorrhea
- Pituitary insufficiency
- Chronic illness or extreme stress
3. Poor Ovarian Reserve
- Infertility
- Low AMH, low antral follicle count
4. Anorexia / Malnutrition
- Low body fat reduces aromatization
High Estradiol Levels
1. Ovarian Hyperstimulation / Ovulation Induction
- During IVF
- Risk of OHSS when very high
2. Estrogen-Secreting Tumors
- Granulosa cell tumor
- Sertoli-Leydig tumors
3. PCOS
- Mild–moderate elevation
- Altered LH/FSH ratio
4. Pregnancy
- Estradiol increases progressively
- Placenta becomes major source
5. Liver Disease
- Reduced estrogen metabolism
6. Gynecomastia in Men
- Increased aromatization
- Testicular tumors
- Medications (spironolactone, HRT)
Reference Intervals
(Tietz 8E + Endocrine Society + ASRM + Mayo + ARUP)
Estradiol varies strongly with sex, age, and menstrual cycle phase.
Women (pg/mL)
Follicular Phase:
- 20 – 150 pg/mL
Mid-Cycle Peak (Ovulation):
- 150 – 750 pg/mL
Luteal Phase:
- 30 – 450 pg/mL
Postmenopause:
- < 10 – 30 pg/mL
Men
- 10 – 40 pg/mL
Children
- Prepubertal: <10 pg/mL
- Early puberty: 10–50 pg/mL
- Late puberty: 20–200 pg/mL
Diagnostic Uses
1. Menstrual Cycle & Ovulation Assessment
- Detects follicular maturity
- Used in ovulation induction cycles
- Assesses response in fertility treatments
2. Infertility Workup
- Estradiol + AMH + AFC → ovarian reserve
- High E2 → PCOS
- Low E2 → ovarian insufficiency
3. Pubertal Disorders
- Precocious puberty
- Delayed puberty
- Gonadal failure
4. Menopause Diagnosis
Low E2 + high FSH confirms ovarian failure.
5. Tumor Marker
For:
- Granulosa cell tumors
- Feminizing tumors
6. Gynecomastia Evaluation in Men
E2 included in hormonal panel.
7. Endocrine Disorders
Used in:
- PCOS
- Hyperprolactinemia
- Thyroid disorders
Analytical Notes
- Serum sample
- Diurnal variation minimal compared to progesterone
- Cycle-day specificity important
- Immunoassays often imprecise at very low levels
- LC-MS/MS preferred for male, pediatric & postmenopausal levels
- Biotin supplements may cause assay interference
Clinical Pearls
- Estradiol peaks just before ovulation (~200–400 pg/mL).
- In IVF, E2 > 3000 pg/mL indicates risk of OHSS.
- Anestrous estradiol <10 pg/mL defines menopause biochemically.
- High estradiol in men warrants evaluation for testicular tumors or liver disease.
- Estradiol must always be interpreted with FSH, LH, and progesterone.
Interesting Fact
Estradiol is so potent that 1 mg of estradiol contains more biological activity than grams of other steroids, making it one of the most powerful endogenous hormones.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Steroid Hormones.
- Endocrine Society Guidelines - Female Hormone Testing.
- ASRM Reproductive Endocrinology Standards.
- AACE/ACE Hormone Evaluation Guidelines.
- Mayo Clinic Laboratories - Estradiol.
- ARUP Consult - Estradiol Interpretation.
- MedlinePlus / NIH - Estradiol Test.