임신 및 각종 갑상선질환에서 갑상선 기능 판정에 관한 연구 : 혈청유리 T4의 진단적 의의에 관한 고찰 The diagnostic value of free thyroxine by RIA = Thyroid Function Test in Thyroid Diseases and Pregnancy

다국어 초록 (Multilingual Abstract)

To evaluate the diagnostic accuracy of the measurement of free thyroxine(FT4) by radioimmunoassay, we measured free T4 and T4, T3, T3RU, TSH and TBG serum levels by radioimmunoassay in 18 healthy persons and 52 patients with various thyroid diseases and 11 normal pregnant women.
The results are as follows.
1) In 19 cases of overt hyperthyroidism, T3, free T4 and FTI, T4/TBG ratio reflect hyperfunction in all cases. T4 is increased in 94%(18/19) and TBG and TSH are decreased in 79%(15/19).
2) In 8 patients with overt hypothyroidism, TSH is increased in all cases and free T4 and FTI is decreased in all cases. T4 is decreased in 87.5%(7/8), T3 is decreased in 75%(6/8) and T4/TBG ratio is decreased in 62.5%(5/8).
3) In 5 patients who are clinically in euthyroid state after treatment of hyperthyroidism, T4 free T4, FTI and TSH are in the normal range in all cases and T3 is normal in 60%(3/5) and slightly increased in 40%(2/5).
4) In 10 patients who showed clinically borderline hypothyroidism after treatment of hyperthyroidism, TSH is increased in all cases and free T4 and FTI are decreased in all cases, but T4 and T3, T4/TBG ratio are in the normal limit in all cases. So after treatment of hyperthyroidism, TSH, free T4 or FTI are recommended as optimal function test.
5) In normal pregnancy, free T4, FTI and T4/TBG ratio reflect normal function, but the other parameters unreliable due to the influence of increased TBG. Also TBG and TSH level in pregnancy is increased significantly compared with normal healthy control group.
6) The coefficients of correlation between T4 and FTI were 0.862(p〈0.001) and 0.685(p〈0.001) between free T4 and T4/TBG ratio.
In most patients, diagnostic value of free T4 was comparable and even superior to FTI, so free T4 measurement can be used routinely with thyrotropin assay in the diagnosis of hypothyrodism or with T3 for the diagnosis of hyperthyroidism.