PTH and chronic kidney disease: In pediatric CKD patients in stages 2–4, the initiation of active vitamin D sterols is recommended when serum PTH levels exceed the target range for the respective CKD stage (CKD 2–3 35–70 pg/mL, CKD 4 70–110 pg/mL, CKD 5 non in dialysis > 300 pg/mL), provided that 25-hydroxyvitamin D levels are adequate (>30 ng/mL), corrected total serum calcium is below 10 mg/dL and serum phosphate is within the appropriate range for the patient’s age [131].