Sawin C T, Chopra D, Albano J, Azizi F
Ann Intern Med. 1978 Apr;88(4):474-7. doi: 10.7326/0003-4819-88-4-474.
In a large number of normal men (n = 111) and women (n = 110) the free triiodothyronine (T3), index, calculated from serum total T3 and T3-uptake, was highly correlated with free T3, measured by equilibrium dialysis. The correlation was almost as high as that of the free thyroxine (T4) index with free T4. The correlations of the total T3, free T3, and free T3 index with, respectively, the total T4, free T4, and free T4 index were much lower, though still statistically significant. The free T3 index is clinically useful because serum total T3 may sometimes be misleading. Hyperthyroid patients with apparent T4-toxicosis and normal total T3 may have an elevated free T3 index and thus physiologically elevated levels of both thyroid hormones. Calculation of the free T3 index might also make possible the diagnosis of T3-toxicosis in a patient with a normal free T4 index and normal total T3. Total T3 may be elevated without an elevated total T4 in women taking oral contraceptives; thus the free T3 index may prevent a misdiagnosis of T3-toxicosis. The free T3 index seems no better than total T3 in the diagnosis of primary hypothyroidism, but it can confirm the diagnosis of T3-hypothyroidism.
在大量正常男性（n = 111）和女性（n = 110）中，由血清总三碘甲状腺原氨酸（T3）和T3摄取率计算得出的游离T3指数与通过平衡透析法测得的游离T3高度相关。这种相关性几乎与游离甲状腺素（T4）指数和游离T4之间的相关性一样高。总T3、游离T3和游离T3指数分别与总T4、游离T4和游离T4指数之间的相关性则低得多，不过仍具有统计学意义。游离T3指数在临床上很有用，因为血清总T3有时可能会产生误导。表现为T4中毒且总T3正常的甲状腺功能亢进患者，其游离T3指数可能会升高，因此两种甲状腺激素的生理水平都会升高。计算游离T3指数还可能有助于诊断游离T4指数和总T3均正常的患者的T3中毒。服用口服避孕药的女性可能出现总T3升高而总T4不升高的情况；因此，游离T3指数可以防止误诊为T3中毒。在原发性甲状腺功能减退症的诊断中，游离T3指数似乎并不比总T3更好，但它可以确诊T3型甲状腺功能减退症。
