Mohr V S, Barlow J W, Topliss D J, O'Dea K, Stockigt J R
Ewen Downie Metabolic Unit, Alfred Hospital, Melbourne Vic., Australia.
Clin Endocrinol (Oxf). 1987 May;26(5):531-40. doi: 10.1111/j.1365-2265.1987.tb00808.x.
Low serum total T4 associated with subnormal concentrations of thyroxine binding globulin (TBG) has been reported in up to 40% of euthyroid Australian aborigines. It has been suggested that these subjects show both diminished concentration of TBG and reduced TBG affinity for T4 (Sarne et al., 1985). We have compared 12 euthyroid aborigines with low T4 (total T4 44 +/- 5 nmol/l) and aborigines with normal T4 (T4 99 +/- 9 nmol/l, n = 12) using measurements of free T4 and T3 by equilibrium dialysis. TBG was measured both by RIA (Henning, Berlin, FRG) and a method dependent on T4 binding (Corning Immophase). Aborigines with low T4 showed lower levels of free T4 (12.6 +/- 0.6 cf. 18.7 +/- 1.0 pM), free T4 index (66 +/- 8 cf. 98 +/- 13), total T3 (1.1 +/- 0.2 cf. 1.6 +/- 0.3 nmol/l), TBG RIA (14.0 +/- 0.6 cf. 25.0 +/- 1.2 ng/l), and TBG Immophase (9.0 +/- 0.5 cf. 22.0 +/- 1.2 mg/l) (P less than 0.01), but free T3 (5.3 +/- 0.4 cf. 4.7 +/- 0.4 pM) and TSH (1.9 +/- 0.2 cf. 1.8 +/- 0.2 mU/l) were not significantly different from the values found in aborigines with normal T4. Scatchard analysis of T4 and T3 binding was performed using serum diluted 1 : 20,000 for T4 and 1 : 500 for T3 (barbitone buffer pH 8.6, 4 degrees C, dextran-coated charcoal separation). In euthyroid low T4 aborigines compared to those with normal T4, both T4 capacity (106 +/- 14 cf. 238 +/- 13 nM, P less than 0.01) and affinity (5.05 X 10(10) cf. 8.47 X 10(10) M-1, P less than 0.05) were significantly reduced. Similarly, both T3 capacity (62 +/- 10 cf. 154 +/- 16 nM, P less than 0.01) and affinity (1.67 X 10(9) cf. 2.28 X 10(9) M-1, P less than 0.02) were reduced. A substantial minority of euthyroid Australian aborigines have a TBG variant characterized by both reduced capacity and affinity of T4 and T3. These findings suggest that TBG may be both qualitatively and quantitatively abnormal in these subjects.
据报道，在多达40%的甲状腺功能正常的澳大利亚原住民中，血清总T4水平较低且甲状腺素结合球蛋白（TBG）浓度低于正常水平。有人提出，这些受试者的TBG浓度降低且对T4的亲和力也降低（萨内等人，1985年）。我们使用平衡透析法测量游离T4和T3，比较了12名甲状腺功能正常但T4水平较低（总T4 44±5 nmol/l）的原住民和T4水平正常（T4 99±9 nmol/l，n = 12）的原住民。通过放射免疫分析法（德国柏林亨宁公司）和一种依赖T4结合的方法（康宁免疫相法）测量TBG。T4水平较低的原住民的游离T4水平（12.6±0.6对比18.7±1.0 pM）、游离T4指数（66±8对比98±13）、总T3（1.1±0.2对比1.6±0.3 nmol/l）、TBG放射免疫分析法测量值（14.0±0.6对比25.0±1.2 ng/l）和TBG免疫相法测量值（9.0±0.5对比22.0±1.2 mg/l）均较低（P<0.01），但游离T3（5.3±0.4对比4.7±0.4 pM）和促甲状腺激素（TSH）（1.9±0.2对比1.8±0.2 mU/l）与T4水平正常的原住民的值无显著差异。使用稀释1:20000的血清进行T4结合分析，稀释1:500的血清进行T3结合分析（巴比妥缓冲液pH 8.6，4℃，葡聚糖包被活性炭分离）。与T4水平正常的原住民相比，甲状腺功能正常但T4水平较低的原住民的T4结合容量（106±14对比238±13 nM，P<0.01）和亲和力（5.05×10¹⁰对比8.47×10¹⁰ M⁻¹，P<0.05）均显著降低。同样，T3结合容量（62±10对比154±16 nM，P<0.01）和亲和力（1.67×10⁹对比2.28×10⁹ M⁻¹，P<0.02）也降低。相当一部分甲状腺功能正常的澳大利亚原住民有一种TBG变体，其特征是对T4和T3的结合容量和亲和力均降低。这些发现表明，这些受试者的TBG在质量和数量上可能均异常。
