Estradiol

Estrogens are responsible for the development of the secondary female sex characteristics. Estradiol is a C18 steroid hormone of the estrogen family and constitutes the major gonadal steroid involved in the pubertal growth spurt in females. Like other steroid hormones, estradiol is derived from cholesterol. Estrogens are secreted primarily by the ovarian follicles and the corpus luteum in healthy women, and during pregnancy by the placenta. The adrenal glands and testes (in men) also secrete minute quantities of estrogens.

The major fraction of estradiol (about 97 %) circulates in blood bound with high affinity to sex-hormone binding globulin (SHBG) and with lower affinity to albumin. The unbound fraction (between 1–3 %) is considered to be the biologically active fraction.

The determination of estradiol is used as an aid in diagnosis and monitoring of fertility disorders in the hypothalamus-pituitary-gonad axis estrogen-producing ovarian and testicular tumors, gynecomastia, for the assessment of ovarian function, and for monitoring fertility therapy.

In women with absent menstrual cycles (primary and secondary amenorrhea) or irregular menstrual cycles, estradiol measurements in addition to other hormones (such FSH and TSH) are recommended to identify hyper- or hypoestrogenic states and their possible cause. An Endocrine Society clinical practice guideline recommends the measurement of estradiol as a test to assist in diagnosing hypothalamic amenorrhea as a differential diagnosis to PCOS as well as primary ovarian insufficiency.

Testing for fractionated serum estrogens may be necessary for patients suspected of having disordered steroid metabolism. If a clinician has ordered "total estrogen" follow these steps: 1) SPS calls clinician to inform them that total estrogen is not available, but estradiol is available. 2) If clinician does not want estradiol testing and wishes to pursue other estrogen testing, they must page the LMR. 3) The LMR can approve fractionated serum estrogens from Mayo (Unit code 84230) for patients with suspected disordered steroid metabolism.

Estradiol reference ranges for Adult Females:

• Follicular Phase : 2 -297 pg/mL
• Luteal Phase: 13-347 pg/mL
• Postmenopausal: <72 pg/mL

Estradiol reference ranges for Adult Males:

• 22-50 yrs: 11-45 pg/mL
• 51-70 yrs: 12-45 pg/mL

Note: Estrogen concentrations for patients undergoing gender-affirming treatment should be interpreted based on patient goals and physical response. The reference ranges provided may not align with the target goals for an affirmed gender.

Specimen requirements:

• Preferred: 4 mL GOLD SST tube.
• Acceptable: RED TOP, GREEN TOP, and LAVENDER TOP tube.

Unacceptable: LIME GREEN TOP

Note: The Laboratory MUST process specimen within 2 hours of blood collection.

Centrifuge and separate serum from cells within 2 hours.

Storage stability:

• Ambient (15–25 °C): 5 days
• Refrigerated (2–8 °C): 14 days
• Frozen (−20 °C ± 5 °C): 12 weeks (freeze only once)