SOST and osteoporosis: Rabenhorst et al. compared the levels of bone turnover cytokines, including IL-6, RANKL, OPG, Dkk-1 and SOST, as well as tryptase, calcium, parathormone and vitamin D in the serum of 21 ISM patients with osteopenia or osteoporosis and in healthy volunteers (n = 10).