Postmenopausal Hormone Therapy: An Endocrine Society Scientific Statement -- Concensus Statement/Review

Conclusions:
The major conclusions related to the overall benefits and risks of MHT expressed as the number of women per 1000 taking MHT for 5 yr who would experience benefit or harm. Primary areas of benefit included relief of hot flashes and symptoms of urogenital atrophy and prevention of fractures and diabetes. Risks included venothrombotic episodes, stroke, and cholecystitis. In the subgroup of women starting MHT between ages 50 and 59 or less than 10 yr after onset of menopause, congruent trends suggested additional benefit including reduction of overall mortality and coronary artery disease. In this subgroup, estrogen plus some progestogens increased the risk of breast cancer, whereas estrogen alone did not. Beneficial effects on colorectal and endometrial cancer and harmful effects on ovarian cancer occurred but affected only a small number of women. Data from the various Women's Health Initiative studies, which involved women of average age 63, cannot be appropriately applied to calculate risks and benefits of MHT in women starting shortly after menopause.
At the present time, assessments of benefit and risk in these younger women are based on lower levels of evidence.

Study Finds Breast Cancer Metastasis Increases After Estrogen And Progestin Hormone Therapies

Note: a second study published in Menopause/postmenopausal women/preclinical study

"Although Hyder said that the study was independent of whether or not the ovaries were intact, it's still unclear whether progestins have the same effects in pre-menopausal women.

"Especially if there's a family history of breast cancer, it's advisable not to take progestins. It's a difficult call that must be made on an individual basis by a physician," Hyder said...."