[Action mechanism of the thyroid hormone in the heart cell--interaction of the thyroid hormone and catecholamines].

The thyroid hormones change the adrenergic reactivity of the myocardium. Since a series of cardiac functions, among others also ways of metabolism such as glycogenolysis and lipolysis underlie an adrenergic regulation, changes of the state of the thyroid gland manifest themselves on them. Investigations at the system of the beta-adrenergic receptor-adenylate-cyclase have shown that in hyperthyreosis and the beta-adrenergic number of receptors is increased by more than double. Moreover, references were got that the thyroid hormones have an influence on the coupling of the receptor to the catalytic subunit of the adenylate cyclase and a regulatory subunit of the enzyme which is regulated by guanine nucleotides. These findings help in the clarification of the causes for the changed reaction to the beta-adrenergic stimulation of the heart.