Although research has shown conflicting data about this issue, it is clear that estrogen can cause an already existing breast cancer to grow faster. For this reason it is crucial that all women taking estrogen follow breast cancer screening recommendations carefully. However, most doctors are very careful about insisting that breast exams and mammogram schedules be adhered to in women for whom they prescribe estrogen. For this reason the breast cancer mortality rates in these women have actually been shown to be lower than in women of the same age who do not take estrogen. Estrogens are known to increase the risk of blood clots in women who have a history of blood clotting disorders.
Some women experience puffiness and breast tenderness with estrogen therapy.
Although a small weight gain can be experienced on estrogen therapy, it is usually not more than a few pounds. There is a legitimate concern about estrogen therapy causing uterine cancer if it is taken without adequate progesterone therapy in women with an intact uterus. However, this risk is easily alleviated by adding progesterone therapy as discussed above. Estrogens can cause blood pressure elevation. Your doctor will monitor your blood pressure while on these medications.