Context: Lower-than-commonly-prescribed doses of conjugated equine estrogens (CEEs) with medroxyprogesterone acetate (MPA) improve vasomotor symptoms and vaginal atrophy, provide acceptable bleeding and lipid profiles, and afford endometrial protection. This lower-dose therapy's protection against loss of bone mineral density (BMD) associated with menopause has not been thoroughly investigated.
Objective: To determine the effects of lower doses of CEEs only or CEEs-MPA on spine and hip BMD, total body bone mineral content (BMC), and biochemical markers of bone turnover in postmenopausal women.
Design and setting: Two-year randomized, double-blind, placebo-controlled substudy of the Women's Health, Osteoporosis, Progestin, Estrogen trial, conducted at 19 US centers between August 1995 and October 2000.
Participants: Eight hundred twenty-two healthy postmenopausal women aged 40 to 65 years who were within 4 years of their last menstrual period.
Interventions: Patients were randomly assigned to receive CEEs, 0.625; CEEs, 0.625 and MPA, 2.5; CEEs, 0.45; CEEs, 0.45 and MPA, 2.5; CEEs, 0.45 and MPA, 1.5; CEEs, 0.3; CEEs 0.3 and MPA, 1.5 (all doses in mg/d); or placebo for 2 years. All participants also received elemental calcium at 600 mg/d.
Main outcome measures: Changes from baseline in spine and total hip BMD, total body BMC, and biochemical markers of bone turnover (serum osteocalcin and urinary cross-linked N-telopeptides of type I collagen), assessed at 6-month intervals and compared among treatment groups with a modified intention-to-treat approach.
Results: At 24 months, women assigned to all of the active treatment groups had significant gains from baseline (P<.001) in spine and hip BMD and total body BMC (except total body BMC in the group receiving CEEs, 0.3 mg/d). These changes were significantly different from those in the placebo group, in which losses of bone mass in spine and total body were evident over the course of the study (P<.001). The loss in hip BMD from baseline in the placebo group was significant at 18 (P =.02) but not at 24 months (P =.06). Osteocalcin and N-telopeptides of type I collagen were significantly reduced from baseline (P<.001) for all active treatment groups at all time points; no changes were found for the placebo group. For women treated with CEEs alone, the gains in spine BMD for the group taking CEEs, 0.625 mg/d, were significantly higher than those of the group taking CEEs, 0.3 mg/d (P =.02), but not the group treated with CEEs, 0.45 mg/d (P =.48).
Conclusions: Doses of CEEs or CEEs-MPA lower than 0.625 mg/d effectively increase BMD and BMC in early postmenopausal women.