Elevation of serum alkaline phosphatase (ALP) level in postmenopausal women is caused by high bone turnover

Most of the alkaline phosphatase (ALP) isoenzymes are derived from the bones and liver. High levels of ALP are often encountered during routine blood investigation in elderly patients. However, because ALP includes various isoenzymes from other tissues, an accurate diagnosis is usually not possible on the basis of elevated ALP alone.To identify the cause of increased ALP in postmenopausal women.We measured serum ALP in a group of 626 postmenopausal osteoporotic women before and after treatment with a bisphosphonate (either alendronate or risedronate). We analyzed the correlations between ALP levels and bone metabolic markers or hepatic function markers.The ALP and BAP levels of people in their 80s were significantly higher than those of people in their 60s. With bisphosphonate therapy, the BAP decreased, and the elevated ALP decreased to normal range levels. ALP was highly and significantly correlated with BAP both before and after treatment. The changes in levels of ALP correlated well with the changes in BAP levels before and after bisphosphonate therapy. Markers of liver function correlated with total ALP (p < 0.01), but the correlation was much smaller than that between ALP and BAP.Bisphosphonate treatment lowered ALP levels, and this decrease was strongly correlated with a decrease in BAP. Among blood test data, the decrease in BAP had the strongest correlation with the ALP decrease.For treatment of osteoporosis, ALP is an acceptable alternative to BAP. Elevated ALP in postmenopausal women is mainly caused by high bone turnover.