Nevertheless, the relationship between FGF23 and these phosphate channels is clear; direct administration of recombinant FGF23 has been seen to reduce renal expression of NPT2A in mice [94], and renal expression of NPT2A and/or NPT2C is downregulated in FGF23-high mice (Hyp or Fgf23-TG) and in patients with XLH [3, 90, 95]. The gene discussed is FGF23; the disease is X-linked hypophosphatemia.