Japanese
Title血中free thyroxineの間接的指標としてのfree thyroxine index, T4 / TBG比およびT4 / unbound TBG比の比較
Subtitle原著
Authors今野則道*, 森川清志**, 今寛*, 萩原康司***, 田口英雄***, 沖田芳夫***
Authors(kana)
Organization*北海道社会保険中央病院内科, **北海道大学医学部第一内科学教室, ***北海道社会保険中央病院放射線科
Journal核医学
Volume19
Number3
Page419-429
Year/Month1982/4
Article原著
Publisher日本核医学会
Abstract「要旨」正常人62名, 甲状腺機能異常症58名(未治療37名, 治療中21名), 非甲状腺疾患19名, 妊婦18名の血清についてT3U(Triosorb-S), T4(RIA), free T4(FT4, Amerlex RIA kit), TBG(RIA), TBG capacity(cellulose acetate電気泳動法)を測定し, free T4 index(FT4I, T4×T3U ratio), T4/TBG, T4/unbound TBGを算出し, これら3者のFT4の間接的指標としての臨床上の有用性を比較検討した. Unbound TBGは(1-T4×T4 bound to TBG(%)/TBG capacity)から算出した. FT4(RIA)とFT4(平衡透析)との相関は良好であり(r=0.94, n=43, p<0.001), TBG濃度とTBG capacityとの相関も高かった(r=0.77, n=157, p<0.001). 1)FT4I, T4/TBGおよびT4/unbound TBGとFT4(RIA)との相関係数は, それぞれ0.89, 0.87および0.86であったが, これを対象別にみると, 甲状腺機能異常症にくらべ, 正常人, 非甲状腺疾患(NTI)および妊婦では低かった. 2)FT4とFT4I, T4/TBGおよびT4/unbound TBGとの回帰直線の勾配は, 甲状腺機能異常症では, 正常人, NTI, および妊婦にくらべ, より急峻であった. 3)各指標とFT4との一致度をみると, 甲状腺機能異常症では, いずれもFT4と良く一致した. また妊婦ではFT4IがFT4の分布にもっとも良く一致した. 一方NTIでは, いずれの指標もFT4の分布とは良く一致しなかった. 以上からFT4I, T4/TBGおよびT4/unbound TBGのいずれも甲状腺機能異常では, そのFT4の変動を反映するが, TBG増多症ではFT4IがFT4の間接的指標として, よりすぐれており, またNTIでは, いずれもFT4の間接的指標としての有用性は低いことが示唆された.
Practice臨床医学：一般
Keywordsfree T4, free T4 index, T4: TBG ratio, T4: unbound TBG ratio, thyroid status, diagnostic aids.
English
TitleFree Thyroxine Index, T4: TBG Ratio, and T4: Unbound TBG Ratio: Which is the Best Parameter for Indirect Measurement of Serum Free Thyroxine Concentration?
Subtitle
AuthorsNorimichi KONNO, Kiyoshi MORIKAWA*, Hiroshi KON, Kohji HAGIWARA, Hideo TAGUCHI, Yoshio OKITA
Authors(kana)
Organization*Department of Internal Medicine and Radiology, Hokkaido Central Hospital for Health Insurance, *1st Department of Internal Medicine, Hokkaido University School of Medicine
JournalThe Japanese Journal of nuclear medicine
Volume19
Number3
Page419-429
Year/Month1982/4
ArticleOriginal article
PublisherTHE JAPANESE SOCIETY OF NUCLEAR MEDICINE
AbstractA measurement of free thyroxine index(FT4I)(T4 multiplied by T3 uptake ratio), T4: thyroxinebinding globulin(TBG)ratio(T4/TBG)and T4: unbound TBG ratio(T4/uTBG)was evaluated for their clinical use as an indirect measure of serum free T4(FT4)concentration. Serum T4, T3U(Triosorb-S), TBG(Riagnost TBG, Behringwerke)and FT4(Amerlex kit, Amersham-radiochemical center)concentrations and TBG capacity(cellulose acetate electropheresis)were measured in 62 normal subjects, 18 patients with hyperthyroisidm, 19 patients with hypothyroidism including 6 subclinical hypothyroidism, 21 patients with treated thyroidal disorders, 19 patients with non-thyroidal illnesses(NTI)and 18 pregnants(3rd trimester). Unbound TBG level was calculated by the equation of uTBG = (1-T4×T4 bound to TBG(%)/TBG capacity). FT4 was also measured by equilibrium dialysis method in 43 sera; the correlation coefficient between FT4 by RIA and equilibrium dialysis was highly significant(r=0.935, P<0.001). The correlation coefficient(r)between TBG concentration and TBG capacity was 0.766(p<0.001, n=157). There was also a highly significant correlation between unbound TBG concentration and reciprocal of T3U ratio(r=0.926, p<0.001, n=157). The correlation coefficients of FT4(RIA)with FT4I, T4/TBG and with T4/uTBG were all highly significant(r=0.89, 0.87 and 0.86 respectively)when the data from all subjects were analyzed together. However, when the data from each group was analyzed seperately, the r was lower in normal subjects(r=0.50-0.55), in NTI(r=0.65-0.81)and in pregnancy(r=0.47-0.62)as compared with that for the thyroidal disorders (r=0.72-0.92). The linear regression line between FT4 and three indirect parameters of FT4 showed that the line for patients with thyroidal disorders had a steeper slope than that for other groups. The distribution of FT4I, T4/TBG and T4/uTBG agreed well with FT4 in thyroidal disorders but not in NTI. In pregnancy where FT4 concentration was all within the normal range, FT4I agreed well with FT4, while T4/TBG and T4/uTBG gave lower values than the normal ranges. These results indicate that a)FT4I, T4/TBG and T4/uTBG are similar in their ability to distinguish between hyperthyroid, normal and hypothyroid persons. b)FT4I is superior to T4/TBG and T4/uTBG as an indirect measure of FT4 in the persons with high TBG concentration. c)In NTI, these parameters are less useful for assessing the FT4 concentration indirectly.
PracticeClinical medicine
Keywordsfree T4, free T4 index, T4: TBG ratio, T4: unbound TBG ratio, thyroid status, diagnostic aids.

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