PTHLH and cancer: In the commoner type of metastasis that is predominantly osteolytic, factors, such as parathyroid hormone-related protein (PTHrP) derived from cancer cells, stimulate osteoblast production of the receptor activator of the nuclear factor-κB ligand (RANKL), which in turn stimulates osteoclast maturation and activity.(10) The increased osteoclast activity leads to increased local bone resorption at a greater rate than attempts at osteoblastic bone formation and repair, with net loss of bone.