Similar to osteoporosis, osteolytic metastases are caused by osteoclast stimulation and not by the direct effects of tumor invasion into bone.8,9 Osteoclast-activating factors, such as parathyroid hormone–related protein and interleukin 11, are released by tumor cells, which then promote the secretion of receptor activator of nuclear factor–κB ligand, which in turn induces the formation of osteoclasts and increases bone resorption.6,8,9,10,12. This evidence concerns the gene IL11 and osteoporosis.