Steady state levels of the mRNAs for alpha 1B, beta 1- and beta 2-adrenergic receptors (alpha 1BAR, beta 1AR, beta 2AR) were quantified by DNA excess solution hybridization assays in the heart, lungs, and liver of rats. Tissues for RNA extraction were obtained from euthyroid and thyroidectomized rats and from thyroidectomized rats treated with a single dose of thyroxine. Thyroidectomy resulted in significant decreases in beta 1AR and beta 2AR mRNAs in heart and lung and alpha 1BAR mRNA in liver, whereas the levels of beta 2AR mRNA in liver and alpha 1BAR mRNA in heart and lung were significantly increased. All these changes were reversed within 20 hours of a single s.c. injection of 1 mg/kg thyroxine. These findings indicate for the first time that thyroid state regulates mRNA levels for adrenergic receptors, and that this regulation is tissue- and receptor-specific. The changes in adrenergic receptor mRNAs correlate with and probably underlie the well documented, thyroid-dependent changes in the cellular densities and physiological reactivities of adrenergic receptors.