[Hypercalcemia in multiple myeloma]

Human myeloma cells have been supposed to produce osteoclast activating factors (OAF) that stimulate osteoclasts. The OAF from myeloma cell lines and freshly isolated myeloma cells has been attributed to TNF beta and IL-1 beta, respectively, although production of these cytokines is still controversial. Because of the bone resorption and latent renal dysfunction, hypercalcemia appears to develop readily in myeloma patients. The level of the cytokine production by myeloma cells appears to be relatively low; however, it may be sufficient to activate osteoclasts, because myeloma cells are present close to them. Recently, PTH-rP has been suggested to be involved in the bone resorption. In addition to conventional treatment of hypercalcemia, bisphosphonate may be a usefull tool to inhibit bone resorption.