The relationship between thyroid function and the renal response to parathyroid hormone.

The effect of thyroid status on renal adenosine 3', 5'-cyclic monophosphate (cyclic AMP) metabolism was assessed by measuring the increase in plasma cyclic AMP concentration following the intravenous administration of parathyroid hormone (PTH) to five hypothyroid and six hyperthyroid patients and seven euthyroid control subjects. PTH caused a rapid, transient increase in the concentration of plasma cyclic AMP which was similar in magnitude and time course in the euthyroid and hyperthyroid groups, but reduced in magnitude in the hypothyroid patients. The magnitude of the plasma cyclic AMP response to PTH was positively related to the free thyroxine index. The results suggest that the development of hypothyroidism may impair the renal response to PTH by affecting the turnover of cyclic AMP in the renal cortex.