AUTHOR=Zhang Han , Che Wenliang , Shi Kuangyu , Huang Yan , Xu Chong , Fei Mengyu , Fan Xin , Zhang Jiajia , Hu Xueping , Hu Fan , Qin Shanshan , Zhang Xiaoying , Huang Qingqing , Yu Fei 

TITLE=FT4/FT3 ratio: A novel biomarker predicts coronary microvascular dysfunction (CMD) in euthyroid INOCA patients

JOURNAL=Frontiers in Endocrinology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2022.1021326

DOI=10.3389/fendo.2022.1021326

ISSN=1664-2392

ABSTRACT=<sec><title>Background</title><p>Ischemia and no obstructive coronary artery disease (INOCA) patients who presented coronary microvascular dysfunction (CMD) demonstrate a poor prognosis, yet the risk factors for CMD remain unclear. Subtle changes in thyroid hormone levels within the normal range, especially the free thyroxine (FT4)/free triiodothyronine (FT3) ratio, have been shown to regulate the cardiovascular system. This prospective study investigated the correlation between FT4/FT3 ratio and CMD in euthyroid patients with INOCA.</p></sec><sec><title>Methods</title><p>This prospective study (<uri xlink:href="https://www.chictr.org.cn/" xmlns:xlink="http://www.w3.org/1999/xlink">www.chictr.org.cn/</uri>, ChiCTR2000037112) recruited patients with myocardial ischemia symptoms who underwent both coronary angiography (CAG) and myocardial perfusion imaging (MPI) with dynamic single-photon emission computed tomography (D-SPECT). INOCA was defined as coronary stenosis&lt; 50% and CMD was defined as coronary flow reserve (CFR)&lt;2.5. All patients were excluded from abnormal thyroid function and thyroid disease history.</p></sec><sec><title>Results</title><p>Among 71 INOCA patients (15 [21.1%] CMD), FT4 and FT4/FT3 ratio in CMD group were significantly higher and both showed significantly moderate correlation with CFR (r=-0.25, p=0.03; r=-0.34, p=0.003, respectively). The ROC curve revealed that FT4/FT3 ratio had the highest efficacy for predicting CMD with an optimized cutoff value&gt;3.39 (AUC 0.78, p&lt;0.001, sensitivity, 80.0%; specificity, 71.4%). Multivariate logistic regression showed that FT4/FT3 ratio was an independent predictor of CMD (OR 7.62, 95% CI 1.12-51.89, p=0.038, P for trend=0.006).</p></sec><sec><title>Conclusion</title><p>In euthyroid INOCA patients, increased FT4/FT3 ratio levels are associated with the occurrence of CMD, presenting a novel biomarker for improving the risk stratification.</p></sec>