Association between markers of bone loss and urinary lithogenic risk factors in osteopenic postmenopausal women

In this study, we explored if urinary lithogenic risk parameters could have some application for monitoring bone health status. We recruited 20 women with postmenopausal osteopenia and a negative medical history for nephrolithiasis. Markers of lithogenic risk were evaluated on 24-h urine and fastingmorning urine. Serum levels of bone turnover markers (BTM) were measured in fasting-blood samples. We found that cross-linked telopeptide of type I collagen (CTX) was significantly correlated with 24-h calcium excretion. N-terminal propeptide of type I procollagen (PINP) correlated with 24-h excretion of potassium, calcium and citrate. CTX had considerably increased in patients with pH less than 5.5. Low citrate levels (less than 3.3 mmol/24 h) were associated with lower levels of CTX and PINP. Our findings suggest that a low-grade acidosis and some lithogenic risk factors are detectable in a proportion of patients with postmenopausal osteopenia. Further studies are necessary to confirm that this evaluation could be clinically relevant.