Hormone Replacement Therapy (HRT)

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Uterine cancer/endometrial cancer

Taking estrogen alone causes the lining of the uterus to grow. The risk for endometrial cancer is six to eight times higher in women who take estrogen, compared to those who do not.

Progestin works to decrease the lining of the uterus. For women who still have their uterus, most doctors prescribe progestin (a synthetic progesterone) to counteract the effect of the estrogen.

The WHI study did not find any difference in endometrial cancer rates between the women who took hormones and those who did not. Depending on the form of HRT, taking progestin may cause bleeding similar to a period. This combination of estrogen and progesterone may be in the form of one pill, or it may be two separate pills.