What effect can tamoxifen have in postmenopausal women besides blocking estrogen?

Tamoxifen, a selective estrogen receptor modulator (SERM), is primarily used in the treatment of estrogen receptor-positive breast cancer. In postmenopausal women, tamoxifen blocks estrogen receptors in breast tissue, inhibiting the growth of cancer cells. However, it also has estrogen-like effects in other tissues, particularly the endometrium.

The stimulation of endometrial growth occurs because, while tamoxifen acts as an antagonist in breast tissue, it can act as an agonist in uterine tissue. This dual action can lead to increased proliferation of endometrial cells, resulting in potential complications such as endometrial hyperplasia or even endometrial carcinoma in some postmenopausal women. Therefore, the presence of estrogen-like activity in the endometrium is a significant effect of tamoxifen that is clinically relevant.

The other options do not reflect the primary mechanism or side effects of tamoxifen. While tamoxifen can reduce the risk of breast cancer metastasis by blocking estrogen's proliferative effect in breast tissues, its primary noted additional effect in the context of the endometrium is the stimulation of growth. Enhancing microtubule formation is not a characteristic effect associated with tamoxifen, and stating that