Thyroid dysfunction is common in patients with Down syndrome (DS), the most common chromosomal disorder. Thyroid hormones (THs) are important for normal growth, neurodevelopment, and metabolism, highlighting the importance of quantifying the levels in patients with DS. However, current methods possess cross-reactivity that results in inaccuracies in quantification. We aimed at developing a new analytical method for quantifying the total 3,3′,5-triiodo-l-thyronine (TT3), total 3,3′,5,5′-tetraiodo-l-thyronine (TT4), 3,3′,5′-triiodo-l-thyronine, and reverse T3 (rT3) levels using LC–MS/MS. Repeatability and reproducibility with coefficient of variation values of 2–9 and 3–13%, respectively, were acceptable, suggesting that the assay was suitable for measuring serum THs. We measured the serum TH levels of patients with DS but without thyroid dysfunction (age, 3–20 years) and compared the levels to those of controls (patients with idiopathic short stature; age, 3–17 years). When TH levels were summarized by age group, the serum TT4 concentrations were not significantly different between the controls and patients with DS across all age groups. Meanwhile, the serum TT3 concentrations differed according to age. In addition, the serum rT3 concentrations were significantly higher in patients with DS than in controls, except for those in the 12–14 age group. We also calculated the T3/T4 and rT3/T4 ratios to elucidate the reason for the higher rT3 in patients with DS; however, no useful findings were obtained. Thus, further investigation is needed to clarify our findings.

中文翻译：

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唐氏综合征患者使用串联质谱法定量血清甲状腺激素

甲状腺功能障碍在唐氏综合征 (DS) 患者中很常见，这是最常见的染色体疾病。甲状腺激素 (TH) 对正常生长、神经发育和新陈代谢很重要，突出了量化 DS 患者水平的重要性。然而，目前的方法具有交叉反应性，导致量化不准确。我们旨在开发一种新的分析方法，用于定量总 3,3',5-三碘-l-甲状腺原氨酸 (TT3)、总 3,3',5,5'-四碘-l-甲状腺原氨酸 (TT4), 3, 3′,5′-三碘-l-甲状腺素，并使用 LC-MS/MS 逆转 T3 (rT3) 水平。变异系数值分别为 2-9 和 3-13% 的重复性和再现性是可以接受的，这表明该测定法适用于测量血清 TH。我们测量了没有甲状腺功能障碍的 DS 患者（年龄 3-20 岁）的血清 TH 水平，并将其与对照组（特发性身材矮小患者；年龄 3-17 岁）的水平进行了比较。当按年龄组总结 TH 水平时，所有年龄组的对照组和 DS 患者的血清 TT4 浓度没有显着差异。同时，血清TT3浓度因年龄而异。此外，除了 12-14 岁年龄组之外，DS 患者的血清 rT3 浓度显着高于对照组。我们还计算了 T3/T4 和 rT3/T4 比值，以阐明 DS 患者 rT3 较高的原因；然而，没有得到有用的发现。因此，需要进一步调查以澄清我们的发现。