Thyroid Feedback Quantile-based Index correlates strongly to renal function in euthyroid individuals
Creators: name: Yang, Sijue
name: Lai, Shuiqing
name: Wang, Zixiao
name: Liu, Aihua
name: Wang, Wei
name: Guan, Haixia
Publisher: name: Taylor & Francis
Year: 2021
Subjects: subject: Biochemistry
subject: Medicine
subject: Genetics
subject: FOS: Biological sciences
subject: Neuroscience
subject: Physiology
subject: Chemical Sciences not elsewhere classified
subject: Developmental Biology
subject: Marine Biology
subject: Cancer
subject: Mental Health

description: Previous studies have reported a negative relationship between thyroid-stimulating hormone (TSH) and renal function in euthyroid individuals, but others have found that higher free thyroxine (FT<sub>4</sub>) was associated with an increased risk of chronic kidney disease. This study was designed to analyze the relationship between thyroid and renal function from a new perspective of sensitivity to thyroid hormone. This retrospective study included 2831 euthyroid individuals who underwent a health examination at the First Hospital of China Medical University between January 2017 and December 2018. Parametric Thyroid Feedback Quantile-based Index (PTFQI<sub>FT4</sub>), TSH index (TSHI), thyrotroph T<sub>4</sub> resistance index (TT<sub>4</sub>RI), free triiodothyronine to FT<sub>4</sub> ratio (FT<sub>3</sub>/FT<sub>4</sub>), the secretory capacity of the thyroid gland (SPINA-GT) and the sum activity of peripheral deiodinases (SPINA-GD) were calculated. We also innovated the TT<sub>3</sub>RI and PTFQI<sub>FT3</sub> indices based on FT<sub>3</sub> and TSH. Renal function was assessed by estimated glomerular filtration rate (eGFR) CKD-EPI and creatinine-cystatin C-KDIGO equations. After adjustment of basic characteristics and comorbidities, linear regression showed that eGFR <sub>CKD-EPI</sub> was positively associated with FT<sub>3</sub>/FT<sub>4</sub> (<i>β</i> = 23.31), and inversely correlated to PTFQI <sub>FT4</sub> (<i>β</i>= −2.69) (both <i>p</i> &lt; .001). When comparing the fourth versus the first quartile of PTFQI <sub>FT4</sub>, the odds ratio (OR) for a reduced renal function was 1.89 (95% CI 1.28–2.80), and the OR was 0.64 (95% CI 0.43–0.95) when comparing quartiles of FT<sub>3</sub>/FT<sub>4</sub> (both <i>p</i> <sub>for trend</sub>&lt; .05). In addition, for every 1SD increase in PTFQI <sub>FT4</sub>, the OR for a reduced renal function was 1.27 (95%CI 1.10–1.47). TSHI, TT<sub>4</sub>RI and TT<sub>3</sub>RI also showed a negative correlation to renal function. Similar results were obtained in SPINA-GD as in FT<sub>3</sub>/FT<sub>4</sub>. In euthyroid individuals, decreased sensitivity to thyroid hormone is associated with reduced renal function. The composite PTFQI<sub>FT4</sub> index correlates more strongly to renal function than TSH or T<sub>4</sub> alone.KEY MESSAGESDecreased sensitivity to thyroid hormone is associated with reduced renal function in the euthyroid population.The recently developed composite index PTFQI<sub>FT4</sub> seems to correlate more strongly to renal function than individual TSH or FT<sub>4</sub> parameters.Innovative indices TT<sub>3</sub>RI and PTFQI<sub>FT3</sub> based on the interaction between T<sub>3</sub> and TSH may also reflect sensitivity to thyroid hormone. Decreased sensitivity to thyroid hormone is associated with reduced renal function in the euthyroid population. The recently developed composite index PTFQI<sub>FT4</sub> seems to correlate more strongly to renal function than individual TSH or FT<sub>4</sub> parameters. Innovative indices TT<sub>3</sub>RI and PTFQI<sub>FT3</sub> based on the interaction between T<sub>3</sub> and TSH may also reflect sensitivity to thyroid hormone.