Estradiol

Overview

Estradiol (E2) is the primary biologically active estrogen in premenopausal women, produced mainly by the ovaries, with smaller contributions from adrenal glands and peripheral conversion of androgens. It plays key roles in development of secondary sexual characteristics, regulation of the menstrual cycle, bone metabolism, and cardiovascular and neurological function. High levels may be seen in ovarian hyperstimulation, estrogen-secreting tumors, pregnancy, or exogenous estrogen use, while low levels occur in menopause, primary ovarian insufficiency, hypogonadotropic hypogonadism, or some chronic illnesses. Estradiol measurement is clinically useful for evaluating menstrual and fertility disorders, monitoring assisted reproduction, assessing pubertal development, and managing hormone therapy.

Clinical Use Cases

  • Evaluation of amenorrhea, oligomenorrhea, and anovulatory cycles.
  • Monitoring follicular development and response to controlled ovarian stimulation in assisted reproductive technology.
  • Assessment of ovarian reserve and function (with FSH, LH, AMH).
  • Evaluation of delayed or precocious puberty in children and adolescents.
  • Monitoring feminizing hormone therapy in transgender women and in hypogonadal states.
  • Supporting diagnosis and follow-up of estrogen-producing tumors (e.g., granulosa cell tumors).

Specimen Types

  • Serum.
  • Plasma (laboratory-specific, often EDTA or heparin).

Measurement Methods

  • Automated immunoassays (chemiluminescent or electrochemiluminescent).
  • Radioimmunoassay (RIA) in some laboratories.
  • Liquid chromatography–tandem mass spectrometry (LC‑MS/MS) for high sensitivity and specificity, particularly at low concentrations (children, men, postmenopausal women).

Test Preparation and Influencing Factors

  • For menstrual cycle evaluation, timing is critical: commonly measured on specific cycle days (e.g., day 2–5 for baseline ovarian function, peri-ovulatory for peak levels).
  • Pregnancy, oral contraceptives, and other estrogen- or androgen-containing therapies significantly alter levels and should be documented.
  • Liver disease, obesity, thyroid dysfunction, and certain medications (e.g., aromatase inhibitors, anticonvulsants) can influence estradiol metabolism or binding proteins.
  • Diurnal and cycle-related variation require consistent sampling conditions when monitoring over time.

Synonyms

  • E2.
  • 17β‑Estradiol.
  • Oestradiol (British spelling).

Further Reading