Braun B E, Müller M J, Seitz H J, Krieg M
Clin Chem. 1983 Dec;29(12):2057-60.
Although discrepancies have been reported between free thyroxin (fT4) in serum and actual thyrometabolic status, the concentration of free thyroid hormones in blood is thought to be an important determinant of the thyrometabolic status of patients. Therefore, the diagnostic value of fT4 measurement has been emphasized. This prompted us to evaluate the diagnostic significance of direct fT4 measurement. We conclude that: (a) The different fT4 radioimmunoassays we examined did not excel the total thyroxin, fT4 index, or thyroxin/thyroxin-binding globulin ratio in the laboratory assessment of thyroid status and alterations in thyroid hormone-thyroxin-binding globulin relationships. (b) The fT4 values obtained by direct or indirect methods always shifted in parallel to total thyroxin with respect to borderline increased or decreased total thyroxin, subclinical hypothyroidism, isolated hypertriiodothyroninemia, and thyroxin substitution.
尽管血清中游离甲状腺素（fT4）与实际甲状腺代谢状态之间存在差异的报道，但血液中游离甲状腺激素的浓度被认为是患者甲状腺代谢状态的重要决定因素。因此，fT4测定的诊断价值受到了重视。这促使我们评估直接测定fT4的诊断意义。我们得出以下结论：（a）在甲状腺状态的实验室评估以及甲状腺激素-甲状腺素结合球蛋白关系的改变方面，我们所检测的不同fT4放射免疫分析方法在甲状腺状态评估中并不优于总甲状腺素、fT4指数或甲状腺素/甲状腺素结合球蛋白比值。（b）对于临界性总甲状腺素升高或降低、亚临床甲状腺功能减退、孤立性高甲状腺素血症和甲状腺素替代治疗，通过直接或间接方法获得的fT4值总是与总甲状腺素平行变化。
