Relationship of thyroid function with renal hemodynamics and cholesterol metabolism in proteinuric kidney disease: A pilot study

Abstract Purpose. Nephrotic syndrome and hypothyroidism are respectively reported to influence renal hemodynamic and hypercholesterolemia. However, the relationship of proteinuria-associated thyroid function with renal hemodynamics and cholesterol metabolism has yet to be determined in a simultaneous analysis of thyroid, renal and cholesterol variables. We investigated the hypothesis that the changes in thyroid hormones by proteinuria may contribute to changes in lipid metabolism and renal hemodynamics by proteinuria. Methods. Twenty-nine patients (17 men) with proteinuric kidney disease (mean age 46 years) were enrolled in a pilot study. Data for serum free triiodothyronine (FT3), free thyroxine (FT4), total cholesterol, and filtration fraction (FF; assessed by para-aminohippuric acid clearance) were used in variable-adjusted correlation analyses. Results. The patients had the following data (mean ± standard deviation): urinary protein 5.18 ± 3.28 g/day, FT3 2.18 ± 0.44 pg/mL, FT4 1.03 ± 0.26 ng/dL, FF 0.27 ± 0.07, and total cholesterol 327 ± 127 mg/dL. There was a significant positive correlation of FT3 with FF (β = 0.58, P = 0.01) and a significant inverse correlation of FT4 with total cholesterol (β = -0.40, P = 0.01). Conclusions. The proteinuria associated reduction in serum thyroid hormone levels may be involved in a part of hypercholesterolemia and the impaired glomerular function due to nephrotic syndrome. Further studies of these relationships are required.