Differential diagnosis of hypoparathyroid disorders during childhood.

Changes in the plasma and urinary adenosine 3', 5' monophosphate (cyclic AMP) levels on infusion of parathyroid hormone were studied in 10 normal children, 5 children with idiopathic hypoparathyroidism, and 3 children with pseudohypoparathyroidism. In normal children the plasma concentration of cyclic AMP ranges from 18.0 to 68.0 pmoles/ml under basal conditions, and increases to a peak of about 10-fold the basal level 5 min after infusion of parathyroid hormone. Infusion of parathyroid hormone caused no increase in plasma cyclic AMP in patients with pseudohypoparathyroidism but about 18-fold increase in those with idiopathic hypoparathyroidism. The measurement of plasma cyclic AMP before and 5 min after infusion of parathyroid hormone is concluded to be a single and effective method for differential diagnosis of hypoparathyroid disorders.