The effect of thiazide and loop diuretics on urinary levels of free deoxypyridinoline: An osteoclastic bone-resorption marker

What is known and Objective Diuretics can cause changes in calcium levels due to renal effects. Moreover, calcium levels can also vary as a result of changes in intestinal absorption and in the activity of osteoclastic cells. A marker of osteoclastic bone-resorption activity is the level of urinary free deoxypyridinoline (FDP). Deoxypyridinoline (DP) acts as a cross-link between adjacent collagen chains to provide structural rigidity. Our aim was to investigate the association between use of thiazides and loop diuretics and urinary levels FDP. Methods In this follow-up study, data were obtained from the Rotterdam Study, a large population-based prospective cohort study. For a subset of 658 participants, urinary levels of FDP were measured at baseline. Linear regression analysis was performed to assess the association between the use of thiazides and loop diuretics and the urinary levels of FDP. Results In women, current use of loop diuretics for less than 42 days was associated with an increased level of urinary FDP (+3·43 nmol deoxypyridinoline per mmol urinary creatinine; 95% CI 1·85; 5·02) compared with no use. However, use for a period of more than 42 days was not associated with an increased level of FDP, nor was past use of loop diuretics. For thiazide diuretics, no statistically significant associations were found. What is new and Conclusion In women, short-term use of loop diuretics is associated with an increased level of FDP, reflecting increased bone resorption by osteoclasts. As the difference disappears with longer term use, the clinical significance is unclear and the value of FDP as a biomarker in this setting is not established. The molecular mechanism for the observed differences in bone fracture rates with use of diuretics remains unclear.

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