Taking hormone replacement often will result in either a return in menstrual cycles or unpredictable spotting. Fortunately this effect is usually temporary, and tends to last less than one year. Some of the hormone replacement plans are more likely to cause this than others. Most women who choose not to take hormone replacement therapy do so for fear of cancer. There are two types of cancers that have been a concern, endometrial cancer and breast cancer.
Endometrial cancer can result if estrogen replacement is taken alone, without progesterone.
As long as women take estrogen in combination with progesterone they are not at any extra risk of endometrial cancer. Estrogen taken alone, is usually reserved for women who have had a hysterectomy. We are not certain whether or not hormone replacement causes increased cases of breast cancer. We do know that some types of breast cancer are stimulated to grow in the presence of estrogen. For this reason, women with estrogen positive breast cancer cannot take hormone replacement.