Urinary and nephrogenous cyclic AMP and renal phosphate handling in normal subjects and patients with parathyroid dysfunction

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Abstract
Studies were performed in 60 patients with proven primary hyperparathyroidism pre-operatively and in 54 of these patients post-operatively, 22 patients with permanent hypoparathyroidism and 34 normal subjects. Urinary and nephrogenous cAMP excretion were increased in the hyperparathyroid patients with an overlap of values with the normal group of 10 and 9%, respectively. Values fell in all patients post-operatively, and were decreased in those with permanent hypoparathyroidism. TmPO4/GFR [tubular maximum reabsorptive capacity for phosphate (TmPO4/GFR)] was decreased in the pre-operative hyperparathyroid patients and rose post-operatively, while it was increased in the hypoparathyroid patients with an overlap of values with the normal group of 9%. Post-operative hypocalcemia due to bone hunger was associated with continuing normo- or hypophosphatemia and urinary cAMP that exceeded 4.5 nM/dl GF, while those who developed permanent hypoparathyroidism had hyperphosphatemia, increased TmPO4/GFR and urinary cAMP that was < 3.5 nM/dl GF. Urinary and nephrogenous cAMP were equally effective in characterizing patients with primary hyperparathyroidism and less effective in distinguishing patients with hypoparathyroidism from normal, while TmPO4/GFR estimates were more effective in delineating the hypoparathyroid state.