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[medical citation needed] Estradiol is not produced in the gonads only; in particular, fat cells produce active precursors to estradiol, and will continue to do so even after menopause. [51] Estradiol is also produced in the brain and in arterial walls. In men, approximately 15 to 25% of circulating estradiol is produced in the testicles.
The estrogen:ER complex binds to specific DNA sequences called a hormone response element to activate the transcription of target genes (in a study using an estrogen-dependent breast cancer cell line as model, 89 such genes were identified). [19] Since estrogen enters all cells, its actions are dependent on the presence of the ER in the cell.
As unopposed estrogen therapy (using estrogen alone without progesterone) increases the risk of endometrial hyperplasia and endometrial cancer in women with intact uteruses, estradiol is usually combined with a progestogen like progesterone or medroxyprogesterone acetate to prevent the effects of estradiol on the endometrium.
The use of high-dose estrogen therapy in breast cancer has mostly been superseded by antiestrogen therapy due to the improved safety profile of the latter. [17] High-dose estrogen therapy was the standard of care for the palliative treatment of breast cancer in women up to the late 1970s or early 1980s. [18
Estrogen is usually only given alone in the setting of a hysterectomy due to the increased risk of vaginal bleeding and uterine cancer with unopposed estrogen. [74] [75] HRT has been more strongly associated with risk of breast cancer in women with lower body mass indices (BMIs). No breast cancer association has been found with BMIs of over 25 ...
Whereas the biological half-life of estradiol given by intravenous injection is about 0.5 to 2 hours, the biological half-life of oral estradiol has a range of 13 to 20 hours due to the large and long-lasting pool of estrogen conjugates that is formed during first-pass metabolism and that serves to continuously replenish circulating estradiol ...
Experts call vaginal estrogen "the holy grail" for its effectiveness in improving vulvar or vaginal itching and burning, painful sex and recurring UTIs.
[1] [6] [7] It is a far less potent estrogen than is estradiol, and as such is a relatively weak estrogen. [ 1 ] [ 7 ] [ 8 ] [ 9 ] According to one in vitro study, the relative binding affinity (RBA) of estriol for the human ERα and ERβ was 11.3% and 17.6% of that estradiol, respectively, and the relative transactivational capacity of estriol ...