Correlation between thyroid stimulating hormone and renal function in euthyroid residents of Japan: Results from the Kyushu and Okinawa population study (KOPS)

Aim: The present large-scale Japanese population study was performed to evaluate the relation between the serum thyroid stimulating hormone (TSH) level and renal function. Methods: Out of 1,374 residents who participated in a free public physical examination between 2010 and 2011, we evaluated the data of 888 participants for whom the serum TSH level and estimated glomerular filtration rate (eGFR) were successfully measured. The participants were categorized into three groups based on TSH levels (normal TSH, ≤2.4; high-normal TSH, 2.5 –4.4; and subclinical hypothyroid, ≥4.5 μIU/mL). Multiple linear regression analysis adjusted for cardiovascular risk factors was performed to determine the relationship between serum TSH level and renal function. Results: The mean±SD TSH level was 2.0±1.4 μIU/mL, and 75.9% (n=674) of the participants had normal, 17.9% (n=159) had high-normal, and 6.2% (n=55) had subclinical hypothyroid TSH levels. The mean eGFR significantly decreased with increased TSH levels (normal TSH, 79.3±14.1; high-normal TSH, 77.4±13.0; and subclinical hypothyroid, 72.3±12.2 mL/min/1.73 m²: P for trend <0.01). Multiple linear regression analysis extracted log-transformed TSH level as an independent factor correlated with eGFR in the high-normal TSH group (beta = −0.18, P=0.02). Conclusions: Our findings demonstrated a significant correlation between serum TSH levels and eGFR in high-normal TSH participants. In healthy individuals, high-normal TSH levels indicate increased the risk of chronic kidney disease.