Alegre M, Meléndez E G, Colón G
Bol Asoc Med P R. 1996 Jan-Mar;88(1-3):12-5.
Hyperthyroxinemia does not always equate to hyperthyroidism. Laboratory tests should always be correlated with the clinical picture. A mismatch should make one doubt true hyperthyroidism. The purpose of our study was to assess the etiology of euthyroid hyperthyroxinemia not associated with estrogen use or pregnancy and to review the outcome of those erroneously treated.
The medical records of thirteen euthyroid patients with non estrogen associated hyperthyroxinemia were reviewed. They had a complete set of thyroid function tests including free T3 and free T4 by membrane dialysis, TRH stimulation test and thyroid hormone binding panel.
Two diagnostic groups were identified: Hyperthyroxinemia secondary to binding abnormalities (7/13), better known as familial dysalbuminemic hyperthyroxinemia (FDH) and hyperthyroxinemia secondary to Thyroid Hormone Resistance (THR) (6/13). The FDH group had an elevated T4 and FTI, with normal T3RU, TSH, TRH stimulation test but an abnormal thyroid hormone binding panel which was used to confirm the diagnosis. The THR group had two laboratory presentations: Four patients presented with all the thyroid hormone tests elevated (T4, T3, T3RU, FTI) including a free T3 and free T4 by membrane dialysis with a normal TSH and TRH stimulation test and a normal T4 binding panel. This presentation is typical for a TRH patient with a nuclear receptor defect where all the precursos to the defect accumulate. Two patients with THR presented elevated T4 and free T4 but normal T3 and free T3, localizing the defect at the level of the active T4 transport mechanism across the cellular membrane. These two patients had a normal TSH, TRH stimulation test and T4 binding panel. Two patients were treated erroneously with radioactive iodine and became extremely hypothyroid in spite of normal TFTs. Very high dose of thyroid hormone replacement were required to restore euthyroidism.
One must suspect these two entities in patients clinically euthyroid who have elevated T4 but non-suppressed TSH. A normal TSH and TRH test confirm euthyroidism. A thyroid hormone binding panel differentiates FDH from THR. Neither group require treatment. If treated erroneously and T4 drops to normal values, one must again induce hyperthyroxinemia to restore euthyroidism in these patients.
甲状腺素血症并不总是等同于甲状腺功能亢进。实验室检查结果应始终与临床表现相结合。若两者不相符，则应怀疑是否为真正的甲状腺功能亢进。我们研究的目的是评估与雌激素使用或妊娠无关的甲状腺功能正常的甲状腺素血症的病因，并回顾那些接受错误治疗的患者的结局。
回顾了13例甲状腺功能正常且甲状腺素血症与雌激素无关的患者的病历。他们进行了全套甲状腺功能检查，包括通过膜透析测定游离T3和游离T4、促甲状腺激素释放激素（TRH）刺激试验以及甲状腺激素结合分析。
确定了两个诊断组：继发于结合异常的甲状腺素血症（7/13），即家族性白蛋白异常性高甲状腺素血症（FDH），以及继发于甲状腺激素抵抗（THR）的甲状腺素血症（6/13）。FDH组的T4和游离甲状腺素指数（FTI）升高，T3树脂摄取试验（T3RU）、促甲状腺激素（TSH）、TRH刺激试验正常，但甲状腺激素结合分析异常，以此确诊。THR组有两种实验室表现：4例患者所有甲状腺激素检查结果均升高（T4、T3、T3RU、FTI），包括通过膜透析测定的游离T3和游离T4，TSH和TRH刺激试验正常，T4结合分析正常。这种表现是具有核受体缺陷的TRH患者的典型表现，缺陷的所有前体物质都会蓄积。2例THR患者T4和游离T4升高，但T3和游离T3正常，提示缺陷位于活性T4跨细胞膜转运机制水平。这2例患者TSH、TRH刺激试验和T4结合分析正常。2例患者接受了错误的放射性碘治疗，尽管甲状腺功能检查结果正常，但仍出现严重甲状腺功能减退。需要非常高剂量的甲状腺激素替代治疗来恢复甲状腺功能正常。
对于临床甲状腺功能正常但T4升高且TSH未被抑制的患者，必须怀疑这两种情况。TSH和TRH试验正常可确认甲状腺功能正常。甲状腺激素结合分析可区分FDH和THR。两组均无需治疗。如果治疗错误且T4降至正常水平，对于这些患者，必须再次诱导甲状腺素血症以恢复甲状腺功能正常。
