Estradiol Test

The test measures the amount of the hormone estradiol in the blood. Estradiol, a form of estrogen and in women, is mostly released from the ovaries and adrenal glands.

Estrone (E1), estradiol (E2), and estriol (E3) are the three major forms of estrogen. Of these, estradiol (E2) is the most potent endogenous estrogen. In nonpregnant females, most of the E2 originates in the ovaries, with smaller contributions from the peripheral tissues. The placenta is an additional source during pregnancy. In males, 75% of E2 is produced from testosterone (and other androgens) by an aromatase-catalyzed reaction in the peripheral tissues and 25% of E2 is produced in the testes.

This test is the most common way to measure levels of estrogen for non-pregnant women.

Estradiol in Women & Men

In women, estradiol plays a key role in:

• Growth of the uterus, vagina and Fallopian tubes
• Changes of the outer genitals
• Breast development
• Distribution of body fat

In men, small amounts of estradiol is released by the testes to prevent sperm from dying prematurely.

Uses of Test

• Evaluation of irregular menses/oligomenorrhea/amenorrhea/hypogonadism
• Evaluation of disorders of puberty (precocious or delayed puberty)
• Infertility assessment and assisted reproduction
• Evaluation of estrogen-producing tumors
• Evaluation of feminization in males

Additional Information

Estradiol (E2) is the most active and predominate form of estrogen in the premenopausal female. E2 is produced from the aromatization of androgens (testosterone and androstenedione) and conversion from estrone in the ovary. It is also produced by peripheral conversion of androgens. Estrone (E1) is produced in the ovary from aromatization of androstenedione and metabolism of estradiol. It is a moderately effective estrogen and is found in lower amounts than E2 in the premenopausal female. Estriol (E3) is a very weak estrogen and is produced peripherally from estradiol and estrone.

In postmenopausal females, the ovary no longer produces estrogen. E1 becomes the predominate estrogen and is derived from peripheral conversion of androstenedione. E2 remains low (less than 20 pg/mL) and is produced from peripheral conversion of E1.

Along with FSH, LH, and progesterone, levels of E2 vary throughout the course of the menstrual cycle. During the follicular phase of the menstrual cycle (first day of menses through ovulation), FSH stimulates the growth of ovarian follicles, especially the dominant follicle, and induces production of estrogen. Once estrogen levels reach a certain value (usually >200 pg/mL), a surge in LH is stimulated and ovulation occurs. Estrogen levels decline but it is still secreted along with progesterone from the corpus luteum in the luteal phase (ovulation to start of menses). If no pregnancy occurs, estrogen and progesterone levels decline and menses begins.

Ultrasensitive estradiol tests more accurately detect lower levels of estradiol and may be useful with infertility studies, evaluation of prepubertal girls, postmenopausal women, or men.