Relationship between Thyroid and Kidney Function: Analysis from the Korea National Health and Nutrition Examination Survey Between 2013 and 2015

Abstract

Introduction: Thyroid function is evaluated by thyroid stimulating hormone (TSH) and free thyroxine (fT4). Although many studies have indicated an intimate relationship between thyroid hormones and kidney functions, reports about the simultaneous evaluation of TSH and fT4 are rare. Objective: We aimed to analyze the association between TSH and kidney function, with emphasis on a potential nonlinear relationship, and identify an independent relationship between fT4 and kidney function. Methods: We reviewed the data of 7,061 subjects in the Korea National Health and Nutrition Examination Surveys who were randomly subsampled for thyroid function evaluation between 2013 and 2015. A total of 5,578 subjects were included in the final analysis, after excluding people < 18 years old, and those with a short fasting time, abnormal fT4 levels, and thyroid disease or related medications. Creatininebased estimated glomerular filtration rate (eGFR) was used to define kidney function. Results: A 1 mmol/L increase of logarithmic TSH was associated with decreased eGFR (β: -1.8; 95% CI -2.3 to -1.2; p < 0.001), according to multivariate linear regression analysis. On the multivariate generalized additive model plot, TSH demonstrated an L-shaped relationship with eGFR, showing a steeper slope for 0-4 mIU/L of TSH. A 1 µg/dL increase of fT4 was also associated with decreased eGFR (β: -7.0; 95% CI -0.94 to -4.7; p < 0.001) on the multivariate linear regression analysis; this association was reversed after adjusting for age. On the mediation analysis, the indirect effect via age and direct effect per 1 µg/dL increase of fT4 on eGFR was 9.9 (8.1 to 11.7, p < 0.001) and -7.1 (-9.3 to -4.8, p < 0.001), respectively. Conclusions: Increased TSH was associated with decreased eGFR, particularly in the reference range. The direct effect of increased fT4 was decreased eGFR, which may be affected indirectly by age.

A Pilot Trial on the Effect of Levothyroxine on Proteinuria in Patients With Advanced CKD

“…14,52,53 It is very important to consider the administration of LVX in patients with CKD and alterations in TSH for a greater benefit in decreasing proteinuria, thus adding the correlation that thyroid hormone in endothelial damage and in cardiovascular risk could also decrease mortality and decrease eGFR. 14,20,52,54 In our study, eGFR increased in the LVX group by 4 ml/min per 1.73 m 2 , compared to that in the placebo group, in which eGFR decreased by 2 ml/min per 1.73 m 2 . Van Welsem et al 9 reported that the normalization of hypothyroidism after treatment with LVX led to a significant improvement in renal function in a patient with CKD.…”

“…With TSH levels between 2.5 and 10.0 mIU/ml, we chose TSH >2.5 mIU/ml, as there is evidence that there was an association of a decrease in eGFR 10,54 Q13 with proteinuria, 10 and TSH <10.0 mIU/ml excludes clinical hypothyroidism. All patients treated with angiotensinconverting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) and without renal replacement therapy who attended the Renal Health Clinic were considered for participation in this pilot clinical trial.…”

Thyroid Feedback Quantile-based Index correlates strongly to renal function in euthyroid individuals

“…However, others have only reported a positive correlation between free triiodothyronine (FT 3 ) and eGFR [ 15 ]. On the contrary, some studies have found that higher free thyroxine (FT 4 ) was associated with decreased eGFR in the euthyroid population [ 16 , 17 ].…”

The Correlation Between Low Serum T3 Levels and All-Cause and Cardiovascular Mortality in Peritoneal Dialysis Patients

“…1 Under conditions such as renal hypofunction, it will also have a greater effect on the synthesis, secretion and clearance of thyroid hormones. 2 On the other hand, thyroid hormones significantly impact renal development and kidney dynamics. 3,4 Elevated TSH, FT4, and reduced T3 levels were associated with reduced kidney function.…”