Plasma cyclic AMP response to glucagon as an index of tissue responsiveness to thyroid hormone.

The rise in plasma cyclic AMP after glucagon has been studied in hyper- and hypothyroid patients before and after treatment. In the hyperthyroid group, each individual patient showed a decrease in cyclic AMP response to glucagon on becoming euthyroid, but there was no change after treatment with propranolol. In the hypothyroid group, each individual patient showed an increase in response on becoming euthyroid on thyroxine. We suggest that peak plasma cyclic AMP response to glucagon could be used to monitor tissue responisveness to thyroid hormone during treatment of hypo- and hyperthyroidism, though change in this response is a more sensitive indicator of change from the hypothyroid to the euthyroid state than from the hyperthyroid to the euthyroid state.