Endocrine therapy Endocrine therapy is also known as anti-hormone therapy. If laboratory tests show that breast cancer cells have hormone receptors, then endocrine therapy may be an option. Endocrine therapy keeps tumor cells from getting or using the natural hormones (estrogen and progesterone) they need to grow. If you are not yet menopause, options for hormone therapy include 1. a drug that blocks the activity of estrogen in the body (tamoxifen) 2. surgical removal of the ovaries (the ovaries produce estrogen) 3. a drug that reduces the amount of estrogen produced by the ovaries (LH-RH agonist LH-RHagonist) If you If you are past menopause, options include 1. a drug that prevents the body from producing estrogen, (aromatase inhibitor) exemestane, letrozole, etc. 2. tamoxifen The side effects of hormone therapy depend on the type of treatment. The most common side effects are hot flashes, vaginal discharge and nausea.