Estradiol

Estradiol is a steroid hormone and the most potent naturally occurring estrogen in humans. It is produced mainly by the ovaries and acts through estrogen receptors throughout the body.

Estrogen receptor: A nuclear receptor activated by estrogens that regulates gene expression and other cellular signaling. Estradiol binds these receptors to alter gene activity and cell function.
Menstrual cycle: The recurring ovarian and uterine changes that prepare the body for possible pregnancy. Estradiol rises during the follicular phase and helps trigger ovulation.
Estrogen: A class of steroid hormones that regulate reproductive development and affect multiple body systems. Estradiol is the most potent naturally occurring human member of this hormone class.
Estriol: A naturally occurring estrogen that is relatively weak outside pregnancy and rises substantially during pregnancy. Unlike estriol, estradiol predominates as the potent estrogen during much of reproductive life.
Aromatase: An enzyme that converts androgens into estrogens. It makes estradiol from testosterone in ovarian and other tissues.
Hormone replacement therapy: Treatment that supplies hormones to relieve symptoms caused by reduced endogenous hormone production. Estradiol is used to treat menopausal symptoms and prevent bone loss in selected patients.
Steroid hormone: A signaling molecule synthesized from cholesterol that can cross cell membranes and bind intracellular receptors. Estradiol’s cholesterol-derived structure gives it its characteristic signaling route.
Progesterone: A steroid hormone that prepares the uterus for pregnancy and supports gestation. Its cycle pattern and reproductive roles complement but differ from estradiol’s.
Steroidogenesis: The biochemical production of steroid hormones from cholesterol. Estradiol is one product of this larger hormone-synthesis network.
Menopause: The permanent cessation of menstruation after ovarian follicular activity declines. Falling ovarian estradiol is associated with many menopausal symptoms.

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