Author(s): Boivin G, Vedi S, Purdie DW, Compston JE, Meunier PJ
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Abstract The beneficial skeletal effects of menopausal estrogen replacement therapy (HRT) are well documented. The role of secondary mineralization of bone as a determinant of bone quality is now well established in postmenopausal women treated with bisphosphonates or SERMs. The aim of present study was to investigate the effect of conventional and high doses of estrogen on the main parameters reflecting the degree of mineralization of bone (DMB). Bone biopsies were obtained from 20 women with osteopenia or osteoporosis before and after 24 months (18 to 38 months) of conventional HRT, and from 19 women who had received high doses of estradiol (implant 100 mg every 3-6 months for 1.5-20 years). DMB parameters (mean DMB, DMB Freq. Max. and Heterogeneity Index of the individual distributions of DMB) were measured using quantitative microradiography in cortical, cancellous, and total bone and expressed as g mineral/cm(3) bone. Values obtained in women before HRT were lower than those reported in pre- and postmenopausal control women. After conventional HRT, there was an increase in mean DMB (total bone) of 4.4 +/- 1.9\% (mean +/- SEM) versus pre-treatment values (4.1 +/- 2.1\% in cortical bone, 4.5 +/- 2.3\% in cancellous bone); these differences did not reach statistical significance (P = 0.055). Results were similar for DMB Freq. Max. but Heterogeneity Index was not significantly changed. After high dose estradiol therapy, mean DMB (total bone) was 6.9 +/- 1.9\% higher than in untreated women (8.6 +/- 2.1\% in cortical bone, 6.5 +/- 2.1\% in cancellous bone); this difference was statistically significant (P = 0.03). Results were similar for DMB Freq. Max. but once again Heterogeneity Index was not significantly modified. The increases in mean DMB were due to a shift of the curves towards high DMB with a decrease of the low DMB values, as confirmed by the absence of changes in the Heterogeneity Index. Estrogen therapy is associated with an increased degree of mineralization of bone induced by a prolongation of secondary mineralization, similar to that observed with other antiresorptive agents. However, this increase was about two-fold lower than that observed after alendronate therapy (10 mg/day/3 years) in postmenopausal osteoporotic women.
This article was published in Bone
and referenced in Pharmaceutica Analytica Acta