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SERUM 1,25-DIHYDROXYVITAMIN D (1,25-(OH)2 D) LEVELS IN CHILDHOOD RENAL DISEASE

The renal 1α-hydroxylation of vitamin D yields 1,25-(OH)2 D, the hormonally active form of the vitamin. Serum levels are markedly reduced in uremic children with demineralization and osteodystrophy (Chesney et al Am J Dis Child 134:135,1980). Using a precise assay, we have measured serum 1,25-(OH)2 D in 27 children with various glomerular (n=15) and tubular (n=12) diseases, not treated with steroids which reduce 1,25-(OH)2D (Chesney et al Lancet II,1123,1978). Serum was obtained in the fasting state on usual diet. Levels were compared to age-matched controls (2-16 yr) and in terms of creatinine clearance using the Schwartz formula based on height and serum creatinine.Patients with clearances >50 ml/min have values not different from normal; from 25-50 ml/min (mean 32) have significant reduction compared to controls (p<.01) and below 25 ml/min have greatly reduced values (p<.001). This data suggests that defective production of 1,25-(OH)2D3 begins at ≃ 35 ml/min/1.73M2 and may be important in the high incidence of osteodystrophy found in children.