The association of the percentage change of bone mineral density and bone markers after one year of hormone replacement therapy in postmenopausal women

ABSTRACT

BACKGROUND: To predict the therapeutic efficacy of osteoporosis, one or two years is needed to evaluate the therapeutic effect by the measurement of bone mineral density(BMD), whereas three to six months is sufficient with bone markers. Using this information, we can change therapeutic plan or modulate drug dosage if necessary. This approach would provide appropriate therapy for osteoporosis. The purpose of this study is to evaluate the association between the percentage change of BMD which was measured by peripheral quantitative computed tomography(pQCT), and bone markers after 1 year of hormone replacement therapy(HRT) in healthy postmenopausal women. METHODS: Bone mineral density of nondominant distal forearm in 89 postmenopausal women was measured by pQCT. We measured serum alkaline phosphatase(ALP) and intact osteocalcin(iOC, Novocalcin) as bone formation markers, urinary deoxypyridinoline(dPyr, PyriLinks-D(TM)) as bone resorption marker by using enzyme immunoassay. After 1 year of HRT, 54 subjects dropped out and 33 subjects were reevaluated. RESULTS: After 1 year of HRT, the drop-out rate was 61%. There was no significant difference in age, age of menopause, years since menopause, initial BMD, initial bone markers between remained and drop out groups. But osteocalcin level was significantly high in remained group(p=0.02). ALP(-27.6 %), iOC(-29.9%), dPyr(-25.2%) were significantly decreased after 1 year of HRT(p0.05). The levels of BMD and bone markers between before and after was significantly correlated, demonstrating the homogeneity of response to HRT. The percentage change of trabecular BMD was negatively correhted with the percentage change of dPyr after HRT(r=-0.45, p=0.01). The variance of the percentage change of dPyr contributed to the percentage change of trabecular BMD by 20%. There was no correlation between the percentage change of total BMD or cortical BMD and the change of ALP, iOC, or dPyr after HRT. CONCLUSIONS: After 1 year of HRT in postmenopausal women, all biochemical bone markers were decreased significantly, whereas only trabecular BMD measured by pQCT was increased significantly. This result suggests that bone markers was more sensitive than BMD to monitor the therapeutic efficacy of HRT. The percentage change of trabecular BMD was correlated with the change of dPyr after HRT only. dPyr might be the most sensitive marker among bone markers tested. Therefore, we can predict the change of BMD after HRT through monitoring the levels of dPyr.