HUMORAL HYPERCALCEMIA OF MALIGNANCY - SOME ENIGMAS ON THE CLINICAL-FEATURES

Humoral hypercalcemia of malignancy (HHM) is a common paraneoplastic s yndrome mediated by tumor-derived parathyroid hormone-related peptide (PTHRP), which bears structural and functional similarities to PTH. Th us the clinical features of HHM are very similar to those of primary h yperparathyroidism (1 degrees HPT), a prototype of humoral hypercalcem ia caused by PTH. On the other hand, HHM syndrome differs from 1 degre es HPT in several aspects, including serum 1,25(OH)(2)D levels, acid-b ase balance, and bone remodeling process, the reason of which remains largely unknown. We approached these questions using a unique animal m odel of HHM, nude rats implanted with PTHRP-overproducing human carcin omas. In this review we will summarize the results and discuss the imp lications in understanding the disease mechanism. (C) 1995 Wiley-Liss, Inc.