Pietras Sara M, Safer Joshua D
Section of Endocrinology, Diabetes, and Nutrition, Boston University School of Medicine, Boston, MA 02118, USA.
Endocr Pract. 2008 Sep;14(6):738-42. doi: 10.4158/EP.14.6.738.
To review the effect of thyroid autoantibodies on thyroid function assays and to present a case in which thyroid autoantibodies resulted in spurious assay readings for both total thyroid hormone levels and thyroid hormone uptake measurements.
We present a detailed case, including serial laboratory data, and review the relevant literature.
A 61-year-old man with a history of autoimmune disease presented for evaluation of abnormal results of thyroid function tests. The patient had been treated for hypothyroidism with levothyroxine and was noted to have an elevated total thyroxine (T4) level in the setting of a low total triiodothyronine (T3) value and a mildly elevated thyrotropin concentration. He had been referred for evaluation of a presumed deiodinase deficiency that impaired conversion of T4 to T3. During treatment with levothyroxine, these test results were confirmed, and the patient was also found to have an elevated T4 uptake. These findings were initially thought to be due to an excess of transthyretin; however, more extensive testing revealed that the patient had an autoantibody to T4 that interfered with the assays for both T4 and T4 uptake.
Autoantibodies to both T3 and T4 have been described. Such antibodies are not uncommon in patients with thyroid disease. On rare occasions, these antibodies may cause spurious assay readings and obscure the diagnosis. To our knowledge, this is the first report in which both the total T4 level and the T4 uptake were elevated because of the presence of autoantibodies. Thyroid hormone autoantibodies must be considered when clinicians encounter patients with unexplained abnormal results of thyroid function tests.
回顾甲状腺自身抗体对甲状腺功能检测的影响，并呈现一例甲状腺自身抗体导致总甲状腺激素水平和甲状腺激素摄取测量出现假性检测结果的病例。
我们呈现一个详细病例，包括系列实验室数据，并回顾相关文献。
一名有自身免疫性疾病病史的61岁男性因甲状腺功能测试结果异常前来评估。该患者曾用左甲状腺素治疗甲状腺功能减退，在总三碘甲状腺原氨酸（T3）值低且促甲状腺素浓度轻度升高的情况下，总甲状腺素（T4）水平升高。他因推测的脱碘酶缺乏导致T4向T3转化受损而被转诊评估。在左甲状腺素治疗期间，这些测试结果得到证实，且该患者还被发现T4摄取升高。这些发现最初被认为是由于转甲状腺素蛋白过多；然而，更广泛的检测显示该患者有一种针对T4的自身抗体，它干扰了T4和T4摄取的检测。
已描述了针对T3和T4的自身抗体。此类抗体在甲状腺疾病患者中并不罕见。在极少数情况下，这些抗体可能导致假性检测结果并掩盖诊断。据我们所知，这是第一例因自身抗体存在导致总T4水平和T4摄取均升高的报告。当临床医生遇到甲状腺功能测试结果异常且无法解释的患者时，必须考虑甲状腺激素自身抗体。
