FGF23 and X-linked hypophosphatemia: The mechanisms that regulate FGF23 secretion in bone cells are only partially known.Lessons from genetic diseases such as XLH and AHRH1 have taught that disturbances in themineralization of the organic matrix surrounding FGF23-producing cells can be a strongstimulus for their FGF23 secretion (Fenget al. 2006).