title: Effect of ritodrine on thyroid hormone concentrations.
abstract: In a clinical study of 17 pregnant women treated with ritodrine, a beta-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 T3 levels could result from adrenergic stimulation, since propanolol, a beta blocking agent, has proved to decrease T3 levels in man. We have observed a significant increase in serum T3 concentrations 24-48 h after the start of the ritodrine treatment. The changes were only temporarely since one week after the start the serum T3 concentrations did not differ significantly from the pre-treatment levels. A decrease in T3 levels was found after discontinuation of treatment. No significant changes were found in T4 and TSH concentrations excluding an influence in ritodrine therapy on the pituitary-thyroid axes. It was concluded that stimulation of type I deiodinase was responsible for the changes in T3. These beta-2-mimetic variations may explain, to a certain degree, the unwanted chronotropic cardiac side effects of ritodrine and necessitates much care in using this therapy in hyperthyroidic patients.
mesh_terms: D000328:Adult; D001835:Body Weight; D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D012312:Ritodrine / Q000494:pharmacology*; D013963:Thyroid Hormones / Q000097:blood*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D013963:Thyroid Hormones; D014284:Triiodothyronine; D013972:Thyrotropin; D012312:Ritodrine; D013974:Thyroxine