DIFFERENCES IN BONE AND VITAMIN-D METABOLISM BETWEEN PRIMARY HYPERPARATHYROIDISM AND MALIGNANCY-ASSOCIATED HYPERCALCEMIA

Bone and vitamin D metabolism are examined in patients with primary hy perparathyroidism (1 degrees HPT), humoral hypercalcemia of malignancy (HHM), and local osteolytic hypercalcemia (LOH) with normal renal fun ction. Among the bone resorption markers, T scores of total deoxypyrid inoline (Dpyd) were highest in HHM and were significantly higher than those in 1 degrees HPT. Among the formation markers, T scores of osteo calcin (OC) were highest in 1 degrees HPT but were negative in HHM. Th e elevation in total Dpyd was associated with an increase in OC in 1 d egrees HPT, and the ratios of total Dpyd/OC were similar to those in c ontrols. In contrast, many patients with HHM and LOH exhibited elevate d total Dpyd and suppressed OC with increased total Dpyd/OC ratios, bu t the ratios varied widely. Serum 1,25-dihydroxyvitamin D [1,25(OH)(2) D] was elevated in 1 degrees HPT but was suppressed in HHM and LOH at any serum Ca levels. These results demonstrate that increased bone res orption is associated with enhanced bone formation in 1 degrees HPT bu t are uncoupled in many of the HHM and LOH patients, and that total Dp yd/OC ratio can be a useful index to estimate the coupling state of bo ne. It is suggested that the reduction in serum 1,25(OH)(2)D cannot be explained by an elevation in serum Ca in HHM and LOH, and that the di fferences in bone and vitamin D metabolism in HHM and LOH from those i n 1 degrees HPT may be caused by a common mechanism such as the secret ion of some cytokines from tumors.