[In vitro studies of the thyroid gland regulation principles and their evaluation].

The free fractions of the thyroid hormone further the metabolism of the body cells and regulate the synthesis of the thyroid hormone. Once the level of FT3 and FT4 decreases. With the help of a liberation of the hormone stimulating the thyroid gland from the anterior lobe of the pituitary gland the lack of thyroid hormone is corrected. The synthesis and secretion of the thyroid gland stimulating hormone is induced by the thyreotropin releasing hormone which is given by the hypothalamus. Moreover, the organism is able as needed to carry out the monodiodation of LT4 to biologically active LT3 or biologically inactive so-called revers T3 (RT3). The estimation of thyroid gland stimulating hormone before and 30 minutes after intravenous application of thyreotropin releasing hormone has its main importance for the early recognition of a disturbance of the regulating circle hypophysis-thyroid gland, above all in the diagnosis of clinically not yet manifest clinical pictures, such as the latent hypothyreosis and the latent hyperthyreosis, respectively (Basedow hyperthyreosis and thyroidal autonomy). According to the questioning the estimations of the levels of the thyroid hormones and of the thyroid gland stimulating hormone should be used stepwise.