Measurement of estriol in the saliva is used to predict preterm delivery in pregnant women at increased risk. In non-pregnant women, it is commonly used to monitor hormone levels when using estrogen-containing supplements during hormone replacement therapy.
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Estriol is a female steroid hormone that is highly associated with pregnancy and fetal development. The hormone DHEA-S produced in the adrenal glands of the developing fetus is metabolized in the fetal liver to 16-alpha-hydroxy-DHEA-S, which is then converted to estriol in the placenta. By the second trimester of pregnancy, about 90% of the estriol produced comes from fetal DHEA-S. Maternal circulating estriol levels increase progressively during pregnancy, peaking in the third trimester. Estriol production depends on the integrity of the fetoplacental unit. Measurement of estriol levels in the mother's saliva has been used to monitor the condition of the fetus during pregnancy. Estriol measurement is also used as part of various tests (triple and quadruple) to detect certain genetic disorders in the fetus (e.g., Down syndrome, spina bifida, etc.).
The regular role of estriol in non-pregnant women is not fully understood and is under investigation. Regarding estrogenic action, estriol is generally less potent than estradiol or estrone. In non-pregnant women, estriol levels are similar to those of pre-menopausal and post-menopausal women and those of men.
Changes in the levels of estriol and other estrogens may be related to the development of various cancers. Estriol also appears to be associated with certain autoimmune diseases, such as multiple sclerosis and systemic lupus erythematosus, as pregnant women experience a significant reduction in symptoms during the last trimester of pregnancy. Estriol regulates bone and lipid metabolism and protects the nerve cells (neurosteroid hormone).
Due to its weak estrogenic action, estriol is sometimes preferred for intravaginal use as an alternative to systemic estrogen therapy in the treatment of vaginal atrophy in postmenopausal women. It is also used in anti-aging creams to replace estrogen in the skin, which is topically lost with advancing age.
In the blood, most estriol is bound to serum proteins, with 14-16% remaining unbound. Unbound estriol enters saliva from the blood through specific intracellular mechanisms and salivary estriol concentrations approach plasma levels of unbound estriol. In saliva, estriol is virtually not binding to proteins. The correlation of estriol measurements in serum and saliva samples is exceptionally high.
Measurements of hormones in saliva are an excellent choice because the sample collection is non-invasive and easy, without the possible complications and inconvenience of blood sampling, while ensuring the sensitivity and accuracy of the measurements.
