각종 갑상선 질환에서 혈청 Thyroxine 결합글로부린 (TBG)의 진단적 의의

Diagnostic Significance of the Serum Thyroxine Binding Globulin(TBG) in Various Thyroid Diseases

In an attempt to evaluate the diagnostic significance of the serum thyroxine binding globulin (TBG) in various thyroid disease states, the authors measured serum $T_3$ uptake, $T_3$, total $T_4\;free\;T_4$, TSH and TBG by radioimmunoassay technique, and calculated the free $T_4$ index$(FT_4I)$ and $T_4/TBG$ ratio in 10 cases of normal subjects, 11 cases of hypothyroidism, 62 cases of euthyroidism and 37 cases of hyperthyroidism. The data were analysed in the aspects of diagnostic significance in each thyroid disease state, and the results were as follows; 1. In 10 cases of normal subjects, serum TBG was $17.4\sim26.8{\mu}g/ml$, $FT_4I$ was $5.1\sim9.7$, and $T_4/TBG$ ratio was $21.9\sim49.9(Mean{\pm}S.D.)$. 2. In 62 cases of euthyroidism with diffuse and nodular goiter, $FT_4I$ was $7.26{\pm}1.82,\;T_4/TBG$ ratio was $31.47{\pm}10.42$, and there were no significant difference from those of normal subjects (p>0.5). 3. In 11 cases of hypothyroidism, the $FT_4I$ was $3.13{\pm}2.15,\;T_4/TBG$ ratio was $11.3{\pm}5.31$, significantly lower than normal controls (p<0.01). 4. In 37 cases of hyperthyroidism, the $FT_4I$ was $30.0{\pm}12.0,\;T_4/TBG$ ratio was $121.4{\pm}62.2$, significantly higher than normal controls (p<0.01). 5. There were significant correlations between the $FT_4I$ and $T_4/TBG$ ratio, total $T_4\;and\;T_4/TBG$ ratio, in each thyroid function states. 6. The $FT_4I$ showed 100% of diagnostic value in hyperthyroidism, 89.2% in euthyroidism, and 80% in hypothyroidism group. The $T_4/TBG$ ratio showed 100% of diagnostic value in hyperthyroidism and hypothyroidism, and 80.6% in euthyroidism group. The above results suggest that $T_4/TBG$ ratio and $FT_4I$ showed same diagnostic value in hyperthyroidism group, but $T_4/TBG$ showed higher diagnostic significance than $FT_4I$ in hypothyroidism.