It won't cause mood swings, and it won't lower your libido. Estrogen is known to promote the growth of breast cancer cells.
Tamoxifen acts as an anti-estrogen, slowing or stopping the growth of the cancer cells.
At the same time, Powles says, it can act like estrogen in other parts of the body, lowering cholesterol and slowing bone loss. In the study, half the women were given tamoxifen, while the others took a sugar pill. They reported back over five years on the frequency of sexual activity, and their pleasure and discomfort during sex. Researchers found no significant difference between the two groups. As expected, users of tamoxifen experienced more hot flashes, night sweats and cold sweats, all common symptoms of reduced estrogen.