Assessment of regional changes in skeletal metabolism following 3 and 18 months of teriparatide treatment

Abstract Teriparatide (TPTD) increases skeletal mass, bone turnover markers, and bone strength, but in vivo effects at individual skeletal sites have not been characterized. Quantitative radionuclide imaging studies reflect bone blood flow and osteoblast activity to assess regional changes in bone metabolism. Changes in bone plasma clearance using technetium‐99m methylene diphosphonate ( 99m Tc‐MDP) were quantified and correlated with changes in bone turnover markers in 10 postmenopausal women with osteoporosis. Subjects underwent bone scintigraphy at baseline and 3 and 18 months after initiating TPTD 20 µg/day subcutaneously. Subjects were injected with 600 MBq 99m Tc‐MDP, and whole‐body bone scan images were acquired at 10 minutes and 1, 2, 3, and 4 hours. Multiple blood samples were taken between 5 minutes and 4 hours after treatment, and free 99m Tc‐MDP was measured using ultrafiltration. The Patlak plot method was used to evaluate whole‐skeleton 99m Tc‐MDP plasma clearance ( K bone ) and derive regional bone clearance for the calvarium, mandible, spine, pelvis, and upper and lower extremities using gamma camera counts. Bone turnover markers were measured at baseline and 3, 12, and 18 months. Median increases from baseline in whole‐skeleton K bone were 22.3% ( p  = .004) and 33.7% ( p  = .002) at 3 and 18 months, respectively. Regional K bone values were increased significantly in all six subregions at 3 months and in all subregions except the pelvis at 18 months. Bone markers were increased significantly from baseline at 3 and 18 months and correlated significantly with whole‐skeleton K bone . This is the first study showing a direct metabolic effect of TPTD at different skeletal sites in vivo, as measured by tracer kinetics. © 2010 American Society for Bone and Mineral Research