Our Pit1 and Pit2 three allele knockout mice may be a good model to separate effects of hypophosphatemia from effects caused by adaptive hormonal changes as a result of hypophosphatemia and improve our understanding of the pathophysiology of the myopathy seen in hypophosphatemic disorders such as HHRH or XLH59. Here, SLC20A2 is linked to hereditary hypophosphatemic rickets with hypercalciuria.