Estriol, Serum


Estriol is one of the three main naturally occurring estrogen hormones in the human body, alongside estradiol and estrone. Estrogens are a group of steroid hormones that play essential roles in the development and maintenance of the female reproductive system and secondary sexual characteristics.


  1. Production: Estriol is predominantly produced during pregnancy, specifically by the placenta. While small amounts of estriol are produced by the ovaries, adrenal glands, and other tissues, its levels increase significantly during pregnancy.

  2. Pregnancy Marker: Estriol is often used as a marker for fetal well-being during pregnancy. The measurement of estriol levels in maternal blood or urine, particularly in conjunction with other hormone levels, helps assess the health and development of the fetus.

  3. Role in Pregnancy: Estriol, along with other estrogens, contributes to the growth and development of the fetus, the maintenance of the placenta, and the preparation of the mother's body for childbirth. Estriol levels increase progressively throughout pregnancy, with the highest concentrations occurring in the third trimester.

  4. Medical Uses: Estriol has been used in hormone replacement therapy (HRT) for postmenopausal women to alleviate symptoms associated with estrogen deficiency. It is considered a weaker estrogen compared to estradiol.

  5. Estrogen Receptor Interaction: Like other estrogens, estriol exerts its effects by binding to estrogen receptors in various tissues. Estrogen receptors are present in the uterus, breast tissue, bones, and other organs.

  6. Postmenopausal Levels: In non-pregnant, postmenopausal women, estriol levels are generally low. Estriol is considered the least potent of the three main estrogens, and its role in non-pregnant states is less significant compared to estradiol.

  7. Diagnostic Testing: Estriol levels can be measured through blood or urine tests. In pregnant women, monitoring estriol levels, along with other hormonal markers, can provide valuable information about the health of the fetus.

It's important to note that while estriol is primarily associated with female reproductive health, small amounts are also present in males. Additionally, the balance and regulation of estrogen hormones are crucial for overall health in both men and women. Any use of estriol or other estrogen-containing medications should be under the guidance of healthcare professionals, particularly when considering hormone replacement therapy or other medical interventions.


Estriol, Serum


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Reference Range(s)

Adult Males ≤0.18 ng/mL
Adult Females (non-pregnant) ≤0.21 ng/mL
  First Trimester ≤2.50 ng/mL
  Second Trimester ≤9.60 ng/mL
  Third Trimester ≤14.60 ng/mL


Fasting Required: No

Turnaround Time: 3 Days

Test Code: 34883

Preferred Specimen: Serum