Abstract
In a clinical study of 17 pregnant women treated with ritodrine, a β 2-sympathomimetic agent used for tocolysis, thyroid hormone status was assessed longitudinally. This was done in order to verify the hypothesis that an increase in T 3 levels could result from adrenergic stimulation, since propranolol, a beta blocking agent, has proved to decrease T 3 levels in man. Indeed, a statistically significant increase in T 3 serum concentration and in T 3 T 4 ratio was found on the second day after the start of treatment with ritodrine (p < 0.02 and < 0.01 respectively). After discontinuation of treatment a decrease in T 3 serum levels, compared to both treatment and pretreatment levels, was observed. The free T 4 concentration showed a significant drop after the first week of treatment (p < 0.01), but no changes were found in T 4 and TSH levels. It was concluded that the β 2-mimetic-mediated changes in thyroid status provide one more reason for restriction of the use of β-mimetic drugs in hyperthyroidic patients and might offer an additional explanation for the undesirable chronotropic cardiac side-effects of the therapy.
Published Version
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