noun, plural: estetrols
An estrogenic hormone with a chemical formula of C18H24O4
Estetrol (E4) is one of the major endogenous estrogens of humans and other vertebrates. Other endogenous estrogens are estrone (E1), estradiol (E2), and estriol (E3). Estetrol is an estrogenic hormone with a chemical formula of C18H24O4.
Estetrol is a sex steroid hormone. It is one of the estrogenic hormones. However, relative to estradiol's binding affinity, the estetrol has less binding affinity to endogenous receptors. Thus, the estetrol is a weak estrogen.
The level of estetrol that is detectable occurs only during pregnancy. The estetrol is produced by the fetal liver. One of the ways to produce estetrol is by the conversion of estradiol and estriol into estetrol through the enzymes, 15α- and 16α-hydroxylases. The estetrols reaches the circulation. They may bind to albumin but not to sex hormone-binding globulin. The physiological functions of estetrols are still unclear. Nevertheless, they are agonist of estrogen receptors and confer estronegic effects, and therefore, they are considered as estrogens.
Estetrol is also produced synthetically for use as a medication for females needing menopausal hormone therapy.