Can hormone treatment cause cancer?

Sometimes: Hormone therapy can be used for a variety of conditions such as thyroid disorders, birth control, menopause, etc. Hormonal therapy is often used as a treatment for cancer by slowing or stopping cancer cells from growing. Sometimes prolonged use of some hormones can actually cause certain cancers to grow, although this is not as common.

Sometimes: Prolonged use of post-menopausal hormone replacement therapy is associated with an increased risk of breast cancer. That doesn't necessarily mean that the hormones "caused" the cancer--they may simply increase the risk in someone who already had other risk factors, such as family history. And not everyone who takes hormone replacement develops breast cancer.

BCPs, too.: This also is true for birth control pills, although the risk seems to go away after 10 years off "the pill".