Estradiol is produced by the adrenals, placenta, and testes, and is the principal estrogen secreted by the ovaries. Over 98% of circulating estradiol is bound to serum proteins, mainly sex hormone-binding globulin (SHBG). Metabolic clearance of estradiol is influenced by conversion to estrone, hydroxylation, and conjugation with sulfate or glucuronide.
Estradiol normally exerts negative feedback on gonadotropin release. However, as estradiol production accelerates with the rapid growth of the dominant follicle, this feedback becomes positive, triggering a surge in LH secretion and ovulation. Measurement of estradiol is useful in evaluating menstrual dysfunctions, including delayed puberty, amenorrhea, and menopause.
≤ –20 °C; avoid repeated freeze–thaw cycles. For short-term storage (≤8 hours), samples may be kept at room temperature (15–30 °C); for up to 48 hours, refrigerate at 2–8 °C.
Hemolyzed or unspun specimens (may yield inaccurate results)
Enhanced chemiluminescence.
| Category | Estradiol (pg/mL) |
| Female, mid-follicular | 27–122 |
| Female, peri-ovulatory peak | 95–433 |
| Female, mid-luteal | 49–291 |
| Postmenopausal female | <20–40 |