TNFRSF11B and osteoporosis: Mast cell-derived mediators and cytokines may exert a direct stimulatory effect on osteoblast recruitment, proliferation, and activity, while tryptase may increase osteoprotegerin, reducing osteoclast activity and favouring osteosclerosis rather than osteoporosis (Johansson et al. 1996; Chiappetta and Gruber 2006; Gregson et al. 2013).