Nagamine Tomoko, Noh Jaeduk Yoshimura, Emoto Naoya, Kogai Takahito, Hishinuma Akira, Okajima Fumitaka, Sugihara Hitoshi
1Department of Endocrinology, Diabetes and Metabolism, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan.
2Department of Internal Medicine, Ito Hospital, Tokyo, Japan.
Thyroid Res. 2019 Oct 25;12:8. doi: 10.1186/s13044-019-0072-2. eCollection 2019.
Resistance to thyroid hormone (RTH) usually features a syndrome of inappropriate secretion of thyroid-stimulating hormone (SITSH) without suppression of the typical high thyroid hormone levels. However, some patients with RTH show thyroid-stimulating hormone (TSH) suppression due to thyrotoxicosis. We report a case of painless thyroiditis in a patient with RTH that was misdiagnosed as Graves' disease because of TSH-suppressed thyrotoxicosis.
A sixteen-year-old boy consulted a local general physician for fatigue. He had a goiter, and biochemical analysis showed TSH < 0.1 μIU/mL, free triiodothyronine (FT3) of 2.70 pg/mL, and free thyroxine (FT4) of 3.6 ng/dL. He was diagnosed with Graves' disease and was treated with 20 mg thiamazole. One year later, he was referred to the department of endocrinology because of SITSH. He was finally diagnosed with RTH due to the finding of a heterozygous missense mutation (methionine 334 threonine) in the thyroid hormone receptor β gene. Three years after cessation of thiamazole, his hyperthyroxinemia showed marked exacerbation with TSH suppression. We diagnosed him with painless destructive thyroiditis because of low technetium-99 m (Tc-99 m) uptake in the thyroid. Extreme hyperthyroxinemia was ameliorated, with a return to the usual SITSH levels, within 1 month without any treatment.
The present case demonstrates that diagnosing RTH is difficult when patients show hyperthyroxinemia with complete suppression of TSH to undetectable levels, and the data lead to misdiagnosis of RTH as Graves' disease. The initial diagnosis is important, and Tc-99 m scintigraphy is useful for the differential diagnosis of thyrotoxicosis accompanying RTH.
甲状腺激素抵抗（RTH）通常表现为甲状腺刺激激素不适当分泌综合征（SITSH），且典型的高甲状腺激素水平未被抑制。然而，一些RTH患者因甲状腺毒症而出现促甲状腺激素（TSH）抑制。我们报告一例RTH患者发生无痛性甲状腺炎，因其TSH抑制性甲状腺毒症被误诊为格雷夫斯病。
一名16岁男孩因疲劳咨询当地全科医生。他有甲状腺肿大，生化分析显示TSH＜0.1μIU/mL，游离三碘甲状腺原氨酸（FT3）为2.70pg/mL，游离甲状腺素（FT4）为3.6ng/dL。他被诊断为格雷夫斯病，并接受20mg甲巯咪唑治疗。一年后，他因SITSH被转诊至内分泌科。由于在甲状腺激素受体β基因中发现杂合错义突变（甲硫氨酸334苏氨酸），他最终被诊断为RTH。停用甲巯咪唑三年后，他的甲状腺素血症明显加重，伴有TSH抑制。由于甲状腺99m锝（Tc-99m）摄取低，我们诊断他为无痛性破坏性甲状腺炎。在未进行任何治疗的情况下，极端甲状腺素血症在1个月内得到改善，恢复到通常的SITSH水平。
本病例表明，当患者出现甲状腺素血症且TSH完全抑制至无法检测水平时，诊断RTH很困难，这些数据会导致RTH被误诊为格雷夫斯病。初始诊断很重要，Tc-99m闪烁扫描对伴有RTH的甲状腺毒症的鉴别诊断很有用。
