Lithium does not inhibit the parathyroid hormone-mediated rise in urinary cyclic AMP and phosphate in humans.

To test the hypothesis that lithium is a general inhibitor of hormone-activated adenylate cyclase, we infuse parathyroid hormone (PTH) into human subjects prior to and during lithium carbonate administration. PTH infusion caused a significant increase in urinary cyclic AMP and urinary phosphate excretion. There was no significant difference in these responses in the lithium compared to the control period. In four patients with primary hyperparathyroidism, lithium had no significant effect on serum calcium or phosphate or on tubular reabsorption of phosphate. The data do not substantiate the hypothesis that lithium (at therapeutic concentrations) is a general inhibitor of hormonally-activated adenylate cyclase, nor do they support its potential clinical utility in primary hyperparthyroidism.