Bone turnover markers are correlated with total skeletal uptake of 99mTc-methylene diphosphonate (99mTc-MDP)

22 postmenopausal women (52–80 years) volunteered to participate. Scintigraphy was performed by injecting 520 MBq of 99mTc-MDP and taking whole body images after 3 minutes, and 5 hours. TSU was calculated from these two images by taking into account the urinary loss and soft tissue uptake. Bone turnover markers used were bone specific alkaline phosphatase (S-Bone ALP), three different assays for serum osteocalcin (OC), tartrate resistant acid phosphatase 5b (S-TRACP5b), serum C-terminal cross-linked telopeptides of type I collagen (S-CTX-I) and three assays for urinary osteocalcin (U-OC).The median TSU of 99mTc-MDP was 23% of the administered activity. All bone turnover markers were significantly correlated with TSU with r-values from 0.52 (p = 0.013) to 0.90 (p < 0.001). The two resorption markers had numerically higher correlations (S-TRACP5b r = 0.90, S-CTX-I r = 0.80) than the formation markers (S-Total OC r = 0.72, S-Bone ALP r = 0.66), but the difference was not statistically significant. TSU did not correlate with age, weight, body mass index or bone mineral density.In conclusion, bone turnover markers are strongly correlated with total skeletal uptake of 99mTc-MDP. There were no significant differences in correlations for bone formation and resorption markers. This should be due to the coupling between formation and resorption.Bone metabolism can be assessed by biochemical means using bone turnover markers (BTM) measured in serum or urine [1]. BTMs can be used in the monitoring of antiresorptive therapy [2,3] and there is increasing evidence that at least some BTMs can be predictive for bone loss [4] and fracture [5,6]. They are, however, also subjected to rapid changes due to reasons other than bone metabolism [7], such as diurnal variation, other tissue damages and food intake [8]. Some of the BTMs reflect bone formation, while others are associated to bone resorption. However, both formation and resorption markers are usually affected by changes in turnov