ACP5 and postmenopausal osteoporosis: In a previous study of postmenopausal osteoporosis, there was a rapid and significant decline in TRACP-5b levels after the initiation of denosumab treatment, and the rate of change in TRACP-5b levels correlated with changes in serum calcium levels from baseline to 1 week later, suggesting that it may be useful in predicting the development of hypocalcemia [12].