The Korean Journal of Nuclear Medicine (대한핵의학회지)

The Korean Society of Nuclear Medicine (대한핵의학회)
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Thyroid Function Test in Thyroid Diseases and Pregnancy - The diagnostic value of free thyroxine by RIA -

임신 및 각종 갑상선질환에서 갑상선 기능 판정에 관한 연구 - 혈청유리 $T_4$의 진단적 의의에 관한 고찰 -

  • Yoo, M.H. (Department of Internal Medicine, College of Med., Seoul National University) ;
  • Yoon, H.J. (Department of Internal Medicine, College of Med., Seoul National University) ;
  • Shin, Y.T. (Department of Internal Medicine, College of Med., Seoul National University) ;
  • Lee, J.C. (Department of Internal Medicine, College of Med., Seoul National University) ;
  • Chung, S.I. (Department of Internal Medicine, College of Med., Seoul National University) ;
  • Cho, B.Y. (Department of Internal Medicine, College of Med., Seoul National University) ;
  • Lee, M. (Department of Internal Medicine, College of Med., Seoul National University) ;
  • Lee, M.C. (Capital Armed Forces General Hospital)
  • 유명희 (서울대학교 의과대학 내과학교실) ;
  • 윤휘중 (서울대학교 의과대학 내과학교실) ;
  • 신영태 (서울대학교 의과대학 내과학교실) ;
  • 이종철 (서울대학교 의과대학 내과학교실) ;
  • 정순일 (서울대학교 의과대학 내과학교실) ;
  • 조보연 (서울대학교 의과대학 내과학교실) ;
  • 이문호 (서울대학교 의과대학 내과학교실) ;
  • 이명철 (국군수도통합병원)
  • Published : 1981.06.30
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Abstract

To evaluate the diagnostic accuracy of the measurement of free thyroxine (FT4) by radioimmunoassay, we measured free $T_4\;and\;T_4,\;T_3,\;T_3RU$, 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, $T_3,\;free\;T_4$ and FTI, $T_4/TBG$ ratio reflect hyperfunction in all cases. $T_4$ 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 $T_4$ and FTI is decreased in all cases. $T_4$ is decreased in 87.5% (7/8), $T_3$ is decreased in 75% (6/8) and $T_4/TBG$ ratio is decreased in 62.5% (5/8). 3. In 5 patients who are clinically in euthyroid state after treatment of hyperthyroidism, $T_4,\;free\;T_4$, FTI and TSH are in the normal range in all cases and $T_3$ 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 $T_4$ and FTI are decreased in all cases, but $T_4\;and\;T_3,\;T_4/TBG$ ratio are in the normal limit in all cases. So after treatment of hyperthyroidism, TSH, free $T_4$ or FTI are recommended as optimal thyroid function test. 5. In normal pregnancy, free $T_4$, FTI and $T_4/TBG$ ratio reflect normal function, but the other parameters revealed 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 free $T_4$ and FTI were 0.862 (p<0.001) and 0.685 (p<0.001) between free $T_4\;and\;T_4/TBG$ ratio. In most patients, diagnostic value of free $T_4$ was comparable and even superior to FTI, so free $T_4$ measurement can be used routinely with thyrotropin assay in the diagnosis of hypothyrodism or with $T_3$ for the diagnosis of hyperthyroidism.

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