Pathophysiological aspects of recent advances in current thyroid function testing

The paper first discusses thyroid function and thyroid ''status'', which is determined by thyroid gland function in secreting T4, and peripheral bio-transformation of T4. The accuracy of a current in-vitro diagnostic strategy ensures high reliability in clinical routine. More recent test procedures for iodothyronines and immunological phenomena need further evaluation. Later, the bio-transformation of T4 to bioactive and regulatory iodothyronines is discussed with respect to its possible clinical implications. Finally, the significance of TBG in the interpretation of T4 and T3 concentrations is determined and more attention is directed to its functional heterogeneity. (author)