Effects of propranolol and atenolol on plasma and urinary cyclic adenosine 3′,5′-monophosphate in hyperthyroid patients

Abstract

Supine and upright plasma concentrations and the urinary excretion of cyclic adenosine 3\ m=' \ , 5\ m=' \ \ x =r eq-\ monophosphate (cAMP) were studied in 26hyper t hyr oid patients before and during treatment for 3\p=n-\6 days and one month with a non-selective (propranolol, n = 13) or a selective \ g = b \ -l -a d r e n e r g i c antagonist (atenolol, n = 13). Before treatment supine and upright plasma concentrations of cAMP were elevated compared to healthy controls and compared to a re-investigation in the euthyroid state. Propranolol and atenolol both reduced supine and upright plasma cAMP and the reduction persisted during one month of treatment. In five untreated hyperthyroid patients no changes in plasma cAMP were observed between two different investigations. Turning to an upright posture was associated with an increase in plasma cAMP levels in 22 out of the 31 hyperthyroid patients (P < 0.05), while all 11 patients re-examined in the euthyroid state showed a rise in plasma cAMP in the upright position (P < 0.001). The 24 h urinary excretion of cAMP was unaltered during treatment with \g=b\-adrenergic antagonists. The data support earlier findings of stimulation of adrenergic receptor activity by thyroid hormone excess. In hyperthyroidism \g=b\-adrenergicantagonists decrease but do not normalize the activity of the adenylate cyclase system. This reducing effect may be of importance for the alleviation of hyperthyroid symptoms and signs during treatment with \g=b\-adrenergicantagonists.

Thyroid hormones and the adrenergic nervous system

“…Raised plasma cyclic AMP levels have been reported in hyperthyroidism and may serve as indirect proof of increased adrenoceptor activity (35-37). Treatment with both propranolol and the selective@, -adrenoceptor blocking drug atenolol induced clinical amelioration and concomitantly reduced plasma cyclic AMP levels, although plasma cyclic AMP did not reach normal levels (37). Some recent studies have shown that the other selective P,-adrenoceptor blocking drug, metoprolol, effectively controls many clinical manifestations of hyperthyroidism (38,39).…”