High Thyroid-Stimulating Hormone and Low Free Triiodothyronine Levels Are Associated with Chronic Kidney Disease in Three Population-Based Studies from Germany

High serum thyroid-stimulating hormone (TSH) levels have previously been associated with a low estimated glomerular filtration rate (eGFR), but studies associating thyroid hormone levels with albuminuria revealed inconsistent results. We used cross-sectional data from 7933 individuals aged 20 to 93 years of the Berlin Aging Study II and the Study of Health in Pomerania to associate serum TSH, fT3, and fT4 levels with eGFR and albuminuria. In multivariable analyses adjusted for confounding, we found inverse non-linear associations of serum TSH levels with eGFR, while serum fT3 levels showed a positive association with eGFR. High as well as low serum fT4 levels were associated with a lower eGFR. Age but not sex modified the association between thyroid hormone levels and eGFR. The inverse associations between serum TSH levels and eGFR were strongest in the youngest age groups, while the positive associations between serum fT3 levels and eGFR were strongest in older individuals. No significant associations between thyroid hormone levels and albuminuria were found. Our results indicate that hypothyroidism might be associated with a reduced kidney function. Thyroid function might be more tightly related to the eGFR than to albuminuria in the general population.