Testolactone is a medication that is used to treat breast cancer by reducing the amount of estrogen in the body. It works by blocking the production of estrogen in the body, which can help slow or stop the growth of hormone-sensitive tumors. Testolactone is an oral tablet and is typically taken several times a day. It may be used in combination with other treatments for breast cancer. It's important to note that Testolactone is not a commonly used medication, it has been largely replaced by other medications such as aromatase inhibitors.