Endometrial histology and bleeding patterns in menopausal women treated with estrogen and continuous or cyclic progestin

Thirty-six postmenopausal women were randomized to three groups in a double-blind, prospective study. All were treated for three months with conjugated estrogens (Premarin), 0.625 mg daily, and three different doses of a progestin (Provera), 2.5 mg daily, 5 mg daily or 5 mg during the last 12 days of a 28-day cycle. We found that the endometrium was maintained in an inactive phase in 100% of the women given continuous daily progestin but in only 25% of those given cyclic progestin. Bleeding occurred in 100% of subjects given cyclic progestin and in 50% of those given continuous progestin; however, bleeding episodes diminished with time in those on continuous progestin. A hormonal regimen that leads to reduced or absent bleeding and an inactive endometrium is preferable for postmenopausal women if estrogen therapy is to be used for the long term after menopause.