1 University of California, San Francisco
Circulating radioimmunoassayable parathyroid hormone (iPTH) was not present in 30% (117) of 389 normal children tested at ages from cord blood to 17 years. In the other 70% (272), mean iPTH was found to be 25 ± 0.7µl eq/ml (± SEM; range, 0-53 ± 2 SD) . The iPTH levels were elevated in 59% of 24 uremic children without radiologic evidence of osteodystrophy in 94% uremic children with osteodystrophy. Infusion of calcium (10 mg/kg over three hours or 15 mg/kg over four hours) in the children without osteodystrophy reduced the iPTH by nearly 50%; suppression was sustained for 9 to 20 hours. In uremic children with osteodystrophy, similar infusions failed to elevate the serum calcium concentration to the same degree and there was less suppression of iPTH which was not sustained as long. Mean increment in serum calcium observed was 2.1 mg/100 ml with 10 mg/kg/3 hr and 3.4 for 15 mg/kg/4 hr in children without osteodystrophy, and 1.24 and 1.4 mg/100 ml in those with osteodystrophy for similar infusions. In both groups, calcium infusions lowered the concentration of serum magnesium and elevated the serum phosphate concentration. Tubular reabsorption of phosphate did not change consistently despite fall in serum iPTH levels. There was no correlation between suppressibility of parathyroid function and serum creatinine level. In five children with osteodystrophy in whom calcium infusions did not suppress iPTH levels, normal iPTH levels were achieved rapidly after successful renal transplantation. These data indicate that the secondary hyperparathyroidism of uremic children is suppressible and not autonomous.
Submitted on February 13, 1973