PTHLH and neoplasm: Tumor cells in the bone secrete soluble osteoclastogenic factors, including nuclear factor-κB ligand (RANKL), parathyroid hormone-related protein (PTHrP), macrophage-colony stimulating factor (M-CSF), tumor necrosis factors (TNFs) and several interleukins (ILs), resulting in osteoclast activation and an increase in osteoclastic bone resorption.