TNF and periodontitis: The low level of calcium will be responded by the increase secretion of parathyroid hormone, and stimulate the osteoclast to increase calcium blood levels through expressing RANKL.14 Alveolar bone loss in periodontitis is mediated by tumor necrosis factor (TNF)-α, interleukin (IL)-6, RANKL, and prostaglandin E2 (PGE2) as the response to a pathogens.