Effects of alendronate on bone quality and remodeling in glucocorticoid-induced osteoporosis: A histomorphometric analysis of transiliac biopsies

Effects of alendronate (ALN) on bone quality and turnover were assessed in 88 patients (52 women and 36 men aged 22-75 years) who received long-term o ral glucocorticoid exposure. Patients were randomized to receive oral place bo or alendronate 2.5, 5, or 10 mg/day for 1 year and stratified according to the duration of their prior glucocorticoid treatment. Transiliac bone bi opsies were obtained for qualitative and quantitative analysis after tetrac ycline double-labeling at the end of 1 year of treatment. As previously rep orted in glucocorticoid-induced osteoporosis, low cancellous bone volume an d wall thickness were noted in the placebo group as compared with normal va lues. Alendronate treatment was not associated with any qualitative abnorma lities. Quantitative comparisons among the four treatment groups were perfo rmed after adjustment for age, gender, and steroid exposure. Alendronate di d not impair mineralization at any dose as assessed by mineralization rate. Osteoid thickness (O,Th) and volume (OV/BV) were significantly lower in al endronate-treated patients, irrespective of the dose (P = 0.0003 and 0.01, respectively, for O,Th and OV/BV); however, mineral apposition rate was not altered. As anticipated, significant decreases of mineralizing surfaces (7 6% pooled alendronate Group; P = 0.006), activation frequency (-72%; P = 0. 004), and bone formation rate (-71%; P = 0.005) were also noted with alendr onate treatment, No significant difference was noted between the changes ob served with each dose, Absence of tetracycline label in trabecular bone was noted in approximately 4% of biopsies in placebo and alendronate-treated g roups. Trabecular bone volume, parameters of microarchitecture, and resorpt ion did not differ significantly between groups. In conclusion, alendronate treatment in patients on glucocorticoids decreased the rate of bone turnov er, but did not completely suppress bone remodeling and maintained normal m ineralization at all alendronate doses studied. Alendronate treatment did n ot influence the osteoblastic activity, which is already low in glucocortic oid-induced osteoporosis.