Free tetraiodothyronine

They included 330 school-aged children with a mean age of 14. Free triiodothyronine, free tetraiodothyronine and thyrotropin levels, Hb and mean corpuscular volume, Fe and total Fe-binding capacity concentration and ferritin levels were determined. They found that thyroid hormone levels of the children with anemia were not significantly different compared to children without anemia. No significant correlation was found between thyroid hormones and Fe status, and they concluded that the thyroid hormone profile was not significantly affected. As a result, this study showed no correlation between Fe status and thyroid hormone levels. 

In iodine-deficient regions, free tetraiodothyronine (fT4) increases, especially in multinodular goiters, whereas thyroid-stimulating hormone (TSH) levels decrease significantly, especially in multinodular and diffuse goiters (Fassbender et al., 2001). The more contrast agent was used, the more urinary iodine excretion was measured. These observations are probably due to the fact that the thyroid transport mechanism for iodine is not saturated by high-iodine plasma concentrations (Fassbender et al., 2001). The concentration of total T3 remains constant (Fassbender et al., 2001). However, TSH levels decrease in... 

West et al. [188] have used TLC to determine the thyroxine level in human serum. For 43 persons with normal thyroid function they found an average of 5.4 jxg thyroxine per 100 ml serum with a normal range from 3.2 to 7.9 jxg per 100 ml. Altogether 339 patients were examined. ScHOBN and Winkler [148] have reported the radiochromatographic determination of labelled tri- and tetraiodothyronine in the serum of a patient who had been dosed with carrier-free Na I for therapy of hyperthyroidism (Fig. 172). This separation is important because triiodothyronine is about four times as active as tetraiodothyronine. Determination of total hormone iodine in serum with the usual methods does not reveal any pathologically modified ratio of tri- to tetraiodothyronine. 

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