Reduction of urinary calcium/creatinine ratio; The first sign of impaired vitamin D metabolism in children on anticonvulsant therapy

A group of 17 ambulatory children on anticonvulsant therapy for 1-7 years had significantly reduced urinary calcium creatinine ratios. Plasma levels of calcium, phosphate and alkaline phosphatase were normal. Tubular reabsorption of phosphate was similar to that found in the control group. No hyperaminoaciduria or evidence for rickets in wrist X-rays was demonstrated. It is suggested that the enhanced renal tubular reabsorption of calcium compensates for a reduction in gastrointestinal absorption secondary to impaired vitamin D metabolism. The lack of biochemical or radiological evidence for rickets in our patients is most probably the result of the sunny climate in this country.