Indices of intact serum parathyroid hormone and renal excretion of calcium, phosphate, and magnesium.

Up to date reference ranges were established for fasting renal excretion of calcium, phosphorus, and magnesium on 101 healthy children aged 2-15 years. A normal range for intact parathyroid hormone was also measured. The indices of calcium and magnesium excretion showed no correlation with age or sex so that a common range for all children could be established. The 97th centile values for urinary calcium:creatinine and magnesium:creatinine ratios were 0.69 mmol:mmol and 1.05 mmol:mmol respectively. The calculated tubular maximum for phosphate/litre of glomerular filtrate (TmPO4/GFR) showed no correlation with age with a geometric mean value of 1.67 mmol/l. The normal range for intact serum parathyroid hormone for the age group was 11-35 ng/l, which is lower than the adult normal range using the same assay. There was an inverse correlation between TmPO4/GFR and intact parathyroid hormone in this group of normal children.