Clinical and biochemical responses to nadolol and clonidine in hyperthyroidism

Some features of hyperthyroidism mimic sympathetic nervous system overactivity. We have compared the clinical (scored on the Wayne Therapeutic Index), hemodynamic (blood pressure and heart rate) and biochemical (plasma epinephrine, norepinephrine, glucose, free fatty acids, insulin, growth hormone and free thyroxine index) effects of clonidine (alpha 2-agonist, which reduces plasma catecholamine levels) with those of nadolol (non-selective beta adrenergic receptor antagonist) in ten female hyperthyroid patients. Each patient received nadolol for 1 week followed by clonidine for 1 week in a single-blind manner. All measurements were made before treatment and then repeated at the end of the nadolol and clonidine treatment periods. Thyroid function remained unaltered during the study. Both agents caused significant clinical improvement--the mean Wayne Index score was 18 pretreatment, 2 on nadolol and 6 on clonidine (P less than .003 for each). Heart rate was reduced by both drugs, but blood pressure was unchanged. Side effects occurred in eight out of ten patients while on clonidine. Nadolol increased plasma concentrations of epinephrine from 47 +/- 18 pg/mL to 87 +/- 24 pg/mL, and norepinephrine from 241 +/- 154 pg/mL to 338 +/- 224 pg/mL (P less than .001 for each). In contrast, clonidine depressed norepinephrine levels from 241 +/- 154 pg/mL to 110 +/- 49 pg/mL (P less than .001) without lowering plasma epinephrine significantly. Plasma free fatty acids tended to fall on both agents compared to pretreatment levels. The blood glucose, insulin and growth hormone concentrations were unaffected by either drug.(ABSTRACT TRUNCATED AT 250 WORDS)