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The tubular maximum for calcium reabsorption: a normal range in children
N J Shaw1, J Wheeldon, J T Brocklebank
1Department of Paediatrics and Child Health, St James's University Hospital, Leeds, UK.
Objective:
We aimed to establish a normal range for the tubular maximum rate of reabsorption of calcium corrected for glomerular filtration rate.
Design:
A prospective survey was used.
Patients:
One hundred and ten normal children aged 2-14 years were studied.
Measurements:
Total plasma calcium, ultrafiltrable calcium and parathyroid hormone. Urinary calcium, sodium and creatinine excretion.
Results:
The normal range was found to be 1.87-3.39 mmol/l of glomerular filtrate with a geometric mean value of 2.40 mmol/l. There was a significant inverse relationship between the tubular maximum for calcium and the urinary sodium excretion. No significant relationship was found between the tubular maximum for calcium and the level of parathyroid hormone in this group of normal children.
Conclusions:
The normal range seen in children is higher than that seen in adults with a higher mean value. This normal range should be useful in the assessment of renal calcium handling in children with disorders of calcium homeostasis.