Correlation of clinical changes with regard to thyroxine replacement therapy in hypothyroid patients - Focusing on the change of renal function

Thyroid dysfunction has an important role in renal insufficiency. The aim of the study was to correlate the change of renal function with other clinical factors after thyroxine therapy in hypothyroid patients. A prospective study was designed and 30 hypothyroid patients were included. All study subjects received 0.15-0.2 mg/day thyroxine for 12 weeks. Diastolic blood pressure and serum levels of creatine phosphokinase (CPK) and myoglobulin decreased significantly after thyroxine therapy. Serum creatinine decreased (0.87 ± 0.22 vs. 0.70 ± 0.17 mg/dl, p < 0.001) and estimated glomerular filtration rate (eGFR) increased significantly (82.06 ± 31.08 vs. 100.31 ± 31.79 ml/min/1.73 m ²; p < 0.001) after thyroxine replacement. Left ventricular ejection fraction (LVEF) was significantly increased after thyroxine replacement (64.47 ± 11.94 vs. 72.40 ± 13.89%, p = 0.026). No significant vascular functional changes of peripheral (pulse wave velocity) and renal interlobar arteries (pulsatility index and resistance index) were noted. The change of eGFR significantly correlated with the changes of serum-free T ₄ (fT ₄), CPK, myoglobulin and LVEF. The correlation between the change of eGFR and thyroid-stimulating hormone (TSH) level was not significant. In conclusion, the GFR of hypothyroid patients increased significantly after thyroxine replacement. The change of GFR was significantly correlated with the changes of fT ₄, CPK, myoglobulin and LVEF, but not with TSH.