Unaltered lymphocyte beta-adrenoceptor responsiveness in hyperthyroidism and hypothyroidism

Beta adrenoceptor sensitivity may be altered in thyrotoxicosis and myxedema. We therefore studied beta-adrenoceptor responses of peripheral blood lymphocytes to stimulation with 10(-9) to 10(-6) M (-)-isoproterenol from patients before and after treatment of myxedema and thyrotoxicosis as well as in patients without thyroid disease. There were six patients in each group. Lymphocyte basal cyclic adenosine monophosphate (cAMP) concentrations were higher in untreated thyrotoxicosis (4.94 +/- 0.46 pmole/10(6) cells) than in controls (3.47 +/- 0.42 pmole/10(6) cells, p less than 0.05) and in untreated myxedema (3.11 +/- 0.50 pmole/10(6) cells, p less than 0.025). The full isoproterenol dose-response curves were similar in all groups. Calculated maximum velocity (Vmax) showed an approximate increase in cAMP of 14.5 pmole/10(6) cells. Isoproterenol concentrations at half-maximum velocity (EC50) were approximately 10(-8) M. It is concluded that lymphocyte beta 2-adrenoceptor responses are not altered in hypothyroidism and hyperthyroidism.