Biochemical markers of bone remodeling during calcium supplementation in menopausal women; [Les marqueurs biochimiques du remodelage osseux au cours de la supplementation calcique chez la femme apres la menopause]

Bone remodeling markers were measured by in postmenopausal women (mean age ± SD : 64.2 ± 5.0 years) before (MO), after 1 month (M1) and after 2 months (M2) of a daily administration of either calcium (1.200 mg of elemental calcium; n = 18) or placebo (n = 14). The women had normal values of 25 hydroxyvitamin D (2 OHD) (mean ± SD : 14.7 ± 3.7 ng/mL) and a low dietary calcium intake, below the usual values defined as 800 mg/d (mean ± SD : 570 ± 157 mg/d). A decrease of i-PTH levels was observed at M1 (45.1 ± 12.4 pg/mL) and at M2 (41.3 ± 14.5 pg/mL) as compared to MO (48.2 ± 21.1 pg/mL), but without reaching a significant level. The bone formation markers such as osteocalcin (BGA) and bone alkaline phosphatase (BAP) were not significantly decreased during the course of calcium supplementation, their variations expressed as percent from the baseline values were not significantly different between the two groups. The bone resorption markers were decreased with the calcium administration. The reductions of free- deoxypyridinoline (F-Dpd) were not significant, while those of conjugated forms derived from crosslinks (Osteomark® NTX and Crosslaps®: CTX) were highly significant, from M1 (CTX : 249 ± 90 versus 176 ± 533 μg/mmol Cr; P < 0.01 and NTX : 76 ± 41 versus 55 ± 22 nmol BCE/mmol Cr; P < 0.05) also at M2 (CTX : 171 ± 62 μg/mmol Cr; P < 0.01 and NTX 54 ± 23 nmol BCE/mmol Cr; P < 0.05). The variations from baseline were significantly different between calcium and placebo groups at M1 and M2, for NTX and CTX. The 2 month calcium supplementation was responsible for a rapid and sustained decrease of bone resorption markers. The lelopeptide forms were the most sensitive for assessing this modification.