Among physiological reactions of the organism, the multiplicity of action of thyroid hormones is a well known phenomenon. Thyroid hormones (TH) regulate activity of other hormones, receptors for bioactive signals, enzymes, and the function of ion channels. Until triiodothyronine has been identified as a ligand for oncoprotein c-erbA, this broad potency of actions has been mysterious. C-erbA has been recognized to be a transcription factor and an authentic thyroid hormone receptor. Important evidence comes from molecular studies, which have described isoforms of c-erbA and other members of intranuclear receptor family, their heterodimerization, thyroid hormone responsive elements in the target genes, and the existence of the cross-talk mechanism. Till present, much has been learned about TH transcription regulations in vitro. An open question remains whether this regulations are operative also in the intact organism.

Ustav experimentálnej endokrinológie SAV Bratislava