Blood Sciences, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Cambridge, UK.
Ann Clin Biochem. 2021 Jan;58(1):29-37. doi: 10.1177/0004563220969150. Epub 2020 Nov 4.
Reverse T3 (3,3',5'-triiodothyronine or rT3) is the third most abundant iodothyronine circulating in human blood and is produced by the inner ring deiodination of the pro-hormone thyroxine (T4). Unlike the more abundant and active metabolite T3, the measurement of serum rT3 is yet to find a routine clinical application. As rT3 binds weakly to the T3 thyroid nuclear hormone receptors, it is thought to represent an inactive end-product of thyroid hormone metabolism, diverting T4 away from T3 production. The analysis of serum rT3 has, up until recently, been measured by competitive radioimmunoassay, but these methods have been superseded by mass-spectrometric methods which are less susceptible to interference from other more abundant iodothyronines. Serum rT3 concentration is increased as part of the non-thyroidal illness syndrome, and by administration of common medications such as amiodarone which inhibit the metabolism of rT3. Serum rT3 concentration is also affected by genetic conditions that affect the iodothyronine deiodinases, as well as thyroid transporters and transport proteins. Analysis of rT3 can provide a useful diagnostic fingerprint for these conditions. rT3 has been shown to bind extra-nuclear iodothyronine receptors with a potential role in cell proliferation; however, the clinical relevance of these findings awaits further study.
反 T3（3,3',5'-三碘甲状腺原氨酸或 rT3）是人体内循环中第三丰富的碘甲状腺原氨酸，由前体甲状腺素（T4）的内环脱碘产生。与更丰富和更活跃的代谢物 T3 不同，血清 rT3 的测量尚未找到常规的临床应用。由于 rT3 与 T3 甲状腺核激素受体的结合较弱，因此它被认为代表甲状腺激素代谢的无活性终产物，将 T4 从 T3 的产生中转移。直到最近，血清 rT3 的分析一直通过竞争性放射免疫测定法进行测量，但这些方法已被质谱方法所取代，后者不易受到其他更丰富的碘甲状腺原氨酸的干扰。血清 rT3 浓度的增加是非甲状腺疾病综合征的一部分，并且由于使用了胺碘酮等常见药物，这些药物会抑制 rT3 的代谢。血清 rT3 浓度还受到影响甲状腺素脱碘酶、甲状腺转运体和转运蛋白的遗传条件的影响。rT3 的分析可以为这些情况提供有用的诊断指纹。已经表明 rT3 可以与核外碘甲状腺原氨酸受体结合，在细胞增殖中具有潜在作用；然而，这些发现的临床相关性有待进一步研究。
