Incidence of Endometrial Hyperplasia in Postmenopausal Women Taking Conjugated Estrogens (Premarin) with Medroxyprogesterone Acetate or Conjugated Estrogens Alone. The Menopause Study Group

Objective: We evaluated four oral combinations of conjugated estrogens (Premarin) and medroxyprogesterone acetate in preventing endometrial hyperplasia, which can occur with conjugated estrogens alone.

Study Design: This was a 1-year prospective, double-blind, randomized, multicenter study in 1724 postmenopausal women. All five groups took conjugated estrogens (0.625 mg) daily. The respective medroxyprogesterone acetate dosages were 2.5 and 5.0 mg daily (groups A and B) and 5.0 and 10.0 mg for 14 days per 28-day cycle (groups C and D).

Results: Among the 1385 patients with valid biopsy data, endometrial hyperplasia developed in 20% in the conjugated estrogens-treated group and < or = 1% in each of the four conjugated estrogens/medroxyprogesterone acetate-treated groups. The incidence of endometrial hyperplasia did not differ significantly between any of the conjugated estrogens/medroxyprogesterone acetate regimens. However, none of the patients receiving the two higher medroxyprogesterone acetate dosages (groups B and D) had endometrial hyperplasia.

Conclusion: The endometrial hyperplasia incidence was significantly lower in women treated with conjugated estrogens and medroxyprogesterone acetate than in women treated with conjugated estrogens alone.