Estradiol
Estradiol is the most potent form of estrogen. In women, ovaries produce it — levels fluctuate with menstrual cycle and drop at menopause. In men, it comes from converting testosterone via aromatase. Testing helps evaluate menstrual problems, fertility, menopause, and in men — gynecomastia or hormone imbalance. Low estradiol in women may mean menopause, ovarian insufficiency, or hypothalamic suppression. High estradiol in men often relates to obesity or testosterone therapy.
Estradiol (E2) is the most potent and abundant form of estrogen in the body. In women, it’s primarily produced by the ovaries and plays a central role in the menstrual cycle, fertility, and maintaining bone, brain, and cardiovascular health. Estradiol levels fluctuate dramatically throughout the menstrual cycle and decline significantly at menopause. In men, smaller amounts are produced by converting testosterone, and estradiol contributes to bone health, brain function, and sexual function.
Why does this matter? Estradiol testing helps evaluate a wide range of conditions. In women, it’s used to assess menstrual irregularities, fertility problems, menopause symptoms, and monitor hormone therapy or fertility treatments. In men, estradiol testing helps investigate gynecomastia (breast enlargement), sexual dysfunction, or symptoms of hormone imbalance. Because estradiol affects so many body systems, understanding your levels provides important health insights.
Key Benefits of Testing
Estradiol testing provides essential information for evaluating reproductive health in both women and men. In women, it helps assess ovarian function, diagnose causes of irregular periods, evaluate fertility, confirm menopause, and monitor hormone replacement therapy or fertility treatments. In men, testing helps investigate unexplained breast enlargement, sexual dysfunction, or suspected estrogen excess.
For anyone experiencing symptoms of hormone imbalance — whether fatigue, mood changes, bone loss, or sexual problems — estradiol is often a key piece of the diagnostic puzzle.
What Does This Test Measure?
The estradiol test measures the concentration of estradiol (E2) in your blood. Estradiol is one of three estrogens the body produces — the others being estrone (E1) and estriol (E3). Estradiol is the most biologically active and is the primary estrogen during reproductive years.
Where Estradiol Comes From
In women, the ovaries are the main source of estradiol during reproductive years. The developing follicle (egg-containing structure) produces estradiol, with levels rising as the follicle matures. After menopause, the ovaries produce very little estradiol, and smaller amounts come from converting other hormones in fat tissue and adrenal glands.
In men, estradiol is produced primarily through conversion of testosterone by an enzyme called aromatase. This conversion happens in various tissues including fat, brain, and bone. While levels are much lower than in women, estradiol serves important functions in men.
What Estradiol Does
Estradiol has wide-ranging effects throughout the body. In the reproductive system, it drives the menstrual cycle, thickens the uterine lining, maintains vaginal health, and supports fertility. Beyond reproduction, estradiol maintains bone density by inhibiting bone breakdown, protects cardiovascular health through effects on cholesterol and blood vessels, supports brain function including mood and cognition, and helps maintain skin elasticity and thickness.
Estradiol and the Menstrual Cycle
In women with regular cycles, estradiol levels change dramatically throughout the month. Levels are lowest during menstruation, rise progressively during the follicular phase as follicles develop, surge just before ovulation (triggering the LH surge that causes egg release), and remain moderately elevated during the luteal phase before falling if pregnancy doesn’t occur. This cyclical pattern means timing matters when interpreting results.
Why This Test Matters
For Women
Evaluates menstrual irregularities. Estradiol testing helps determine why periods are irregular, absent, or abnormal. Low estradiol may indicate ovarian insufficiency, hypothalamic dysfunction, or menopause. The level helps distinguish between different causes of amenorrhea (absent periods).
Assesses fertility and monitors treatment. Estradiol is routinely measured during fertility evaluations and IVF cycles. Rising estradiol indicates developing follicles. During fertility treatment, estradiol monitoring helps adjust medication doses and determine optimal timing for procedures.
Confirms menopause. Persistently low estradiol along with elevated FSH confirms that menopause has occurred. Testing helps distinguish menopause from other causes of missed periods in women around menopausal age.
Monitors hormone therapy. Women taking estrogen replacement therapy may have estradiol levels checked to ensure appropriate dosing — not too low to be ineffective, not too high to increase risks.
For Men
Investigates gynecomastia. Breast tissue growth in men often relates to estrogen excess or androgen-estrogen imbalance. Elevated estradiol can cause or contribute to gynecomastia and prompts investigation for underlying causes.
Evaluates sexual dysfunction. Both low and high estradiol can affect sexual function in men. Low estradiol may contribute to decreased libido and bone loss, while high estradiol can cause erectile dysfunction and reduced sex drive.
Monitors testosterone therapy. Men on testosterone replacement sometimes develop elevated estradiol from increased aromatization. Monitoring helps identify this and guide treatment adjustments if needed.
Value of Testing
Because estradiol affects bone health, cardiovascular function, mood, and sexual health in both sexes, testing provides valuable information beyond just reproductive concerns. Establishing your baseline and tracking changes over time helps identify developing problems early.
What Can Affect Estradiol Levels?
Causes of High Estradiol in Women
- Normal mid-cycle surge around ovulation
- Pregnancy (estradiol rises significantly)
- Ovarian tumors or cysts producing estrogen
- Estrogen-producing adrenal tumors
- Liver disease (reduced estrogen metabolism)
- Obesity (fat tissue produces estrogen)
- Estrogen therapy or hormone replacement
Causes of Low Estradiol in Women
- Menopause or perimenopause (natural decline)
- Primary ovarian insufficiency (premature ovarian failure)
- Hypothalamic amenorrhea from stress, low weight, or excessive exercise
- Pituitary disorders affecting FSH/LH production
- Polycystic ovary syndrome (some cases)
- Turner syndrome and other genetic conditions
- Chemotherapy or radiation affecting ovaries
Causes of High Estradiol in Men
- Obesity (increased aromatase activity in fat tissue)
- Testosterone therapy (more testosterone available for conversion)
- Liver disease (impaired estrogen metabolism)
- Testicular tumors producing estrogen
- Adrenal tumors
- Certain medications
- Hyperthyroidism
Causes of Low Estradiol in Men
- Hypogonadism (low testosterone means less substrate for conversion)
- Aromatase inhibitor medications
- Genetic conditions affecting estrogen synthesis
Important Timing Considerations
In premenopausal women, estradiol levels vary dramatically with the menstrual cycle. Testing on day 2-4 of the cycle measures baseline ovarian function. Mid-cycle testing captures the pre-ovulatory peak. Random testing without knowing cycle day is difficult to interpret. Your doctor will specify when to test based on what question they’re trying to answer.
When Should You Get Tested?
For Women
Menstrual irregularities: Absent periods, irregular cycles, or unusually light or heavy bleeding warrant evaluation that often includes estradiol.
Symptoms of low estrogen: Hot flashes, night sweats, vaginal dryness, mood changes, or sleep disturbances — particularly around expected menopausal age or in younger women.
Fertility evaluation: Difficulty conceiving or recurrent pregnancy loss. Estradiol helps assess ovarian reserve and function.
During fertility treatment: IVF and other assisted reproduction protocols require estradiol monitoring to track follicle development and adjust medications.
Suspected premature ovarian insufficiency: Menopausal symptoms before age 40 require hormonal evaluation.
Monitoring hormone therapy: Periodic checks help ensure estrogen levels are in the therapeutic range.
For Men
Gynecomastia: Breast enlargement or tenderness warrants evaluation including estradiol.
Sexual dysfunction: Decreased libido, erectile problems, or other sexual symptoms, especially alongside other hormonal symptoms.
Symptoms of hormone imbalance: Fatigue, mood changes, or decreased muscle mass may relate to testosterone-estrogen imbalance.
Monitoring testosterone therapy: Men on TRT may develop elevated estradiol requiring monitoring and potential treatment.
Infertility evaluation: As part of comprehensive male fertility workup.
Understanding Your Results
Estradiol results must be interpreted in context — considering sex, age, menstrual cycle phase (for premenopausal women), symptoms, and other hormone levels. A value that’s normal for one situation may be abnormal for another.
For Premenopausal Women
Results vary dramatically with cycle phase. Early follicular phase (days 2-4) levels reflect baseline ovarian function. Pre-ovulatory peak levels are much higher. Luteal phase levels are moderate. Your doctor interprets results based on when the sample was drawn. Very low levels at any cycle phase suggest ovarian dysfunction or hypothalamic suppression. Extremely high levels outside of expected ovulation timing may indicate ovarian cysts, tumors, or other conditions.
For Postmenopausal Women
Levels are consistently low after menopause. If not taking hormone therapy, estradiol should be quite low. Unexpectedly elevated levels in postmenopausal women not on estrogen therapy warrant investigation for estrogen-producing tumors or other sources.
For Men
Men have much lower estradiol than premenopausal women but require some estradiol for normal function. Low levels may contribute to bone loss and other problems. Elevated levels can cause gynecomastia, sexual dysfunction, and other symptoms. Results are interpreted alongside testosterone and other hormones.
What to Do About Abnormal Results
For High Estradiol
In women: Evaluate for pregnancy first if applicable. Consider timing relative to menstrual cycle. If elevated outside of expected situations, investigate for ovarian cysts or tumors with pelvic ultrasound, liver function, and other testing as indicated. Address modifiable factors like obesity.
In men: Evaluate for underlying causes including liver disease, testicular or adrenal tumors, and medication effects. If related to obesity, weight loss helps reduce aromatization. If occurring on testosterone therapy, dose adjustment or aromatase inhibitors may be considered.
For Low Estradiol
In premenopausal women: Check FSH and LH to distinguish between ovarian failure (high FSH/LH) and hypothalamic/pituitary causes (low or normal FSH/LH). Evaluate for hypothalamic amenorrhea causes — stress, weight loss, excessive exercise. Consider genetic testing if premature ovarian insufficiency is suspected. Hormone replacement may be indicated to protect bones and relieve symptoms.
In postmenopausal women: Low estradiol is expected. Treatment decisions about hormone therapy depend on symptoms and individual risk-benefit assessment.
In men: Low estradiol usually reflects low testosterone, so evaluation and treatment focus on the underlying hypogonadism.
Related Health Conditions
Menopause
Menopause marks the end of ovarian estradiol production, confirmed by persistently low estradiol and elevated FSH. The resulting estrogen deficiency causes hot flashes, vaginal dryness, bone loss, and other changes. Estradiol testing helps confirm menopause and, if hormone therapy is chosen, monitors treatment.
Primary Ovarian Insufficiency
Primary ovarian insufficiency (premature ovarian failure) occurs when ovaries stop functioning before age 40. Low estradiol with elevated FSH confirms the diagnosis. The condition causes infertility and early menopause symptoms, and increases long-term risks from estrogen deficiency. Hormone replacement is usually recommended until typical menopause age. Learn more →
Polycystic Ovary Syndrome (PCOS)
PCOS is a common hormonal disorder causing irregular periods, excess androgens, and often polycystic-appearing ovaries. Estradiol levels in PCOS can be variable — sometimes normal, sometimes showing an abnormal pattern without the usual cyclic changes. Estradiol testing is part of the hormonal evaluation for PCOS.
Hypothalamic Amenorrhea
When stress, low body weight, or excessive exercise suppresses the hypothalamus, it stops signaling the ovaries, causing low estradiol and absent periods. Unlike ovarian failure, FSH and LH are low or normal rather than elevated. Treatment involves addressing the underlying cause — reducing stress, gaining weight, or moderating exercise.
Gynecomastia
Male breast tissue growth results from estrogen-androgen imbalance. Elevated estradiol is one cause, whether from obesity (increased aromatization), liver disease, tumors, or medications. Estradiol testing helps identify hormonal causes and guide treatment.
Osteoporosis
Estrogen is critical for maintaining bone density in both sexes. Estrogen deficiency — whether from menopause, premature ovarian insufficiency, or low estradiol in men — accelerates bone loss and increases fracture risk. Estradiol testing is part of evaluating osteoporosis, especially in premenopausal women or men with unexplained bone loss.
Infertility
Estradiol is central to female fertility, reflecting follicle development and ovarian function. Abnormal estradiol — too low or with abnormal patterns — can indicate ovulatory dysfunction contributing to infertility. During IVF, estradiol monitoring guides treatment decisions. In men, estrogen-testosterone imbalance can also affect fertility.
Related Biomarkers Often Tested Together
FSH (Follicle-Stimulating Hormone) — Works with estradiol to assess ovarian function; high FSH with low estradiol indicates ovarian failure.
LH (Luteinizing Hormone) — Triggers ovulation; tested alongside estradiol for fertility and menstrual evaluations.
Progesterone — Confirms ovulation occurred; tested in luteal phase alongside estradiol.
AMH (Anti-Müllerian Hormone) — Measures ovarian reserve; doesn’t fluctuate with cycle like estradiol.
Testosterone — Evaluated alongside estradiol for hormone balance in both sexes.
Prolactin — Elevated prolactin can suppress estradiol; tested together for amenorrhea evaluation.
Note: Information provided in this article is for educational purposes and doesn’t replace personalized medical advice.
Frequently Asked Questions
Estradiol (E2) is the most potent form of estrogen, the primary female sex hormone. In women, ovaries produce it; in men, it comes from converting testosterone. Estradiol affects reproduction, bones, brain, heart, and many other systems.
It depends on why you’re testing. For baseline ovarian function, days 2-4 of your cycle (early follicular phase). For fertility treatment monitoring, timing follows your protocol. Your doctor will specify when to test based on the clinical question.
Men produce small amounts of estradiol that contribute to bone health, brain function, and sexual function. Too little or too much causes problems. Low estradiol contributes to bone loss; high estradiol can cause breast enlargement and sexual dysfunction.
In premenopausal women, low estradiol may indicate menopause, premature ovarian insufficiency, or hypothalamic suppression from stress or low weight. Causes are distinguished by checking FSH and LH levels. In postmenopausal women, low estradiol is expected.
Yes. In women, very high levels outside of normal ovulation may indicate ovarian cysts, tumors, or liver disease. In men, elevated estradiol causes gynecomastia and other symptoms, often from obesity or testosterone therapy.
At menopause, ovaries stop producing estradiol, so levels drop dramatically and remain persistently low. This causes menopausal symptoms and long-term effects on bones and other tissues.
Yes. Fat tissue contains aromatase, the enzyme that converts androgens to estrogens. More fat means more conversion, raising estradiol levels. This affects both women and men.
References
Key Sources:
- Practice Committee of the American Society for Reproductive Medicine. Testing and interpreting measures of ovarian reserve. Fertil Steril. 2020;114(6):1151-1157.
- The NAMS 2017 Hormone Therapy Position Statement Advisory Panel. The 2017 hormone therapy position statement of The North American Menopause Society. Menopause. 2017;24(7):728-753.
- Camacho PM, et al. American Association of Clinical Endocrinologists/American College of Endocrinology Clinical Practice Guidelines for the Diagnosis and Treatment of Postmenopausal Osteoporosis. Endocr Pract. 2020;26(Suppl 1):1-46.
