A Combination of Low Doses of 17β-Estradiol and Norethisterone Acetate Prevents Bone Loss and Normalizes Bone Turnover in Postmenopausal Women

Abstract:

The effects of 17β-estradiol (E₂) 1 mg combined with low doses of norethisterone acetate (NETA) on postmenopausal bone loss and turnover were investigated in a 2-year, randomized, double-masked, placebo-controlled trial. A total of 135 postmenopausal women with a lumbar spine bone mineral density (BMD) T-score between −2 and +2 were randomized to daily treatment with an oral tablet of either placebo, E₂ 1 mg/NETA 0.25 mg, or E₂ 1 mg/NETA 0.5 mg. Significant (p<0.001) increases in BMD at the lumbar spine (L1–4) were observed with E₂ 1 mg/NETA 0.25 mg (5.2%) and E₂ 1 mg/NETA 0.5 mg (5.4%) compared with placebo (−0.9%). The total hip BMD increased significantly in the E₂ 1 mg/NETA 0.25 mg (3.1%) and E₂ 1 mg/NETA 0.5 mg groups (3.3%) compared with placebo. At the femoral trochanter, the increase in BMD in the E₂ 1 mg/NETA 0.5 mg group (6.3%) was significantly different from the placebo group (0.8%), while that in the E₂ 1 mg/NETA 0.25 mg group (3.3%) was not. No statistical differences were found between the active groups and placebo for the change in BMD at the femoral neck. Significant increases in BMD at the distal radius and total body were found for both E₂ 1 mg/NETA 0.25 mg (0.9% and 2.5%, respectively) and E₂ 1 mg/NETA 0.5 mg (2.1% and 3.0%, respectively) compared with placebo (−0.7% and 0.4%, respectively).

 At the end of the treatment, urinary pyridinoline type I collagen C-telopeptide had decreased by 65% and 60% in the E₂ 1 mg/NETA 0.25 mg and E₂ 1 mg/NETA 0.5 mg groups, respectively, while the mean serum concentrations of osteocalcin had decreased by 39% and 34%, bone-specific alkaline phosphatase by 32% and 29%, and C-terminal propeptide of type I collagen by 21% and 19% had decreased by 34-39%, 29-32%, and 19-21% in the E₂ 1 mg/NETA 0.25 mg and E₂ 1 mg/NETA 0.25 mg groups, respectively.

 In conclusion, combinations of E₂ 1 mg and NETA 0.25 or 0.5 mg prevent bone loss in postmenopausal women at the lumbar spine, hip, distal radius and total body, and normalize bone turnover.