PTHLH and neoplasm: Cytokines such as the receptor activator of nuclear factor-κB (RANK), interleukin-1 (IL-1), IL-6, IL-11, macrophage inflammatory protein 1a (MIP1a), M-CSF, and parathyroid hormone-related peptide (PTHrP) are secreted by osteo-mimicking tumor cells to enhance osteoclast formation and activity, leading to excessive bone resorption (109).