Using Different Doses of Active Vitamin D Combined With Neutral Phosphate in Children With X-linked Hypophosphatemia

Inclusion Criteria: * Male or female, aged 1-12 years, inclusive * Diagnosis of XLH by clinical features: serum phosphorus level \< 2.5 mg/dl; ALP?; RSS total score ≥2; bowed legs; short stature; family history with appropriate X-linked inheritance * Meet at least one of the following: confirmed Phosphate regulating gene with homology to endopeptidases located on the X chromosome (PHEX) mutation in the participant, or serum FGF23 level \>30 pg/ml (Kainos assay) * Willing to participate the study, and provide an informed consent * Able to complete all aspects of study and adhere to the visit schedule Exclusion Criteria: * Use of growth hormone within 12 months before first visit * Height \>50 percentile for age and sex specific data * Presence of nephrocalcinosis or nephrolithiasis * Serum intact parathyroid hormone level\>170 pg/ml * Plan to receive orthopaedic surgery in 12 months * Poor compliance * Use of gonadotropin-releasing hormone therapy right now * Use of aluminium hydroxide, steroid, acetazolamide or thiazide drugs within 7 days before first visit * Not be fit to participant in the study, by the judgement of investigators