Abstract
Estrogens are frequently used in reproductive medicine. The Women’s Health Initiative
trial found that the risks of menopausal hormone therapy (MHT) exceed the benefits.
The estrogens in MHT, however, were introduced prior to our understanding of the mechanism
of action of estrogens. Estrogen signaling is highly complex, involving various DNA
regulatory elements to which estrogen receptors bind. Numerous transcription factors
and co-regulatory proteins modify chromatin structure to further regulate gene transcription.
With a greater understanding of estrogen action, the major problem with the current
estrogens in MHT appears to be that they are nonselective. This produces beneficial
effects in bone, brain, and adipose tissue but increases the risk of breast and endometrial
cancer and thromboembolism. Resurrecting MHT for long-term therapy will require the
development of more selective estrogens, such as estrogen receptor (ER)β-selective
estrogens and tissue-selective ERα agonists. These compounds will offer the best prospects
to expand the indications of MHT and thus prevent the chronic conditions associated
with menopause.
Keywords
estrogen - estradiol - estrogen receptor - gene regulation - transcription