Estriol (E3)

Definition - What does Estriol (E3) mean?

Estriol is one of the three estrogens naturally produced by the body. Estriol is only present during pregnancy, as it is the hormone released by the placenta. Estriol levels may be tested through blood or urine tests.

FertilitySmarts explains Estriol (E3)

Estrogen is one of the two primary sex hormones that exist within a woman’s body (the other being progesterone). While estrogen is present in men’s bodies as well, it is not a dominating developmental player like it is for women. Estrogen is responsible for the female reproductive system, physical features, and controls the menstrual cycle.

There are three types of estrogen hormones: estradiol, estriol, and estrone. Each type corresponds with a life stage: estradiol for young, non-pregnant women, estriol for pregnant women, and estrone for women who have gone through menopause.

The placenta is responsible for the production of estriol. The placenta is the tissue that grows in the uterus, linking a fetus to its mother. Estriol can be identified as early as the 9th week of pregnancy, and the amount secreted increases until the pregnancy is delivered.

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