Estradiol levels are measured in women to assess their reproductive function and health.

Some of the reasons for measuring estradiol are described below:

• In women with amenorrhea (no menstruation) or abnormal menstruation, assessing the level of estradiol can help to diagnose menopause or any underlying disorder of the reproductive system.
• During infertility treatment that involves stimulation of follicular growth to increase ovulation, estradiol is regularly checked as fluctuation in this hormone can disrupt the delicate hormonal balance that is needed for ovulation, preparation of the endometrium and implantation of the fertilized ovum. Assessing estradiol can therefore help to monitor the treatment and predict its success and failure.
• Some forms of cancer and also non-oncogenic conditions rely on the presence of estradiol.
• The blood level of estradiol is raised in a condition called precocious puberty, when menstrual periods start earlier than would be expected, at between 8 to 12 years of age. In cases of delayed puberty, on the other hand, the blood estradiol level is usually low.

Estradiol during the menstrual cycle

In a normal menstrual cycle, estradiol levels fluctuate as follows:

• <50 pg/ml during menstrual periods
• The level rises to up to 200 pg/ml during follicular development.
• Just before ovulation, the level may peak at 400 pg/ml
• The level dips briefly during release of the ovum (ovulation)
• The second estradiol peak occurs during the luteal phase
• In the absence of pregnancy, the level falls to its lowest or menstrual level at the end of the luteal phase.
• If there is a pregnancy, the level rises steadily until the fetus is completely mature. This estradiol arises from the placenta, which aromatizes pro-hormones that come from the adrenal gland of the fetus and convert it to estradiol.

Normal range of estradiol

• In adult males – 14 to 55 pg/mL
• In adult females –
  • Follicular phase (Day 5) – 19 to140 pg/ml
  • Just before ovulation – 110 to 410 pg/mL
  • Luteal phase – 19 to 160 pg/ml
  • After menopause – Less than 35 pg/ml