
Originally Posted by
Swifto
As I've previously stated, the endometrium or uterous is a tissue highely sensitive to estrogen. Tamoxaifen behaves as an agonist, not antagonist. Therfore an upregulation of ER and PgR is seen.
In a normal, healthy subject, Tamoxifen will down regulate the ER in breast tissue. Because the PgR iis synthesised in response to the ER, it follows suit 8-90% of the time.
Some studies show upregulation, but there in breast cancer patients and are not conclusive or consistant at all.