Effects of subclinical hyperthyroidism on renal handling of water and electrolytes in patients with nodular goiter

Summary Evidence is beginning to accumulate that minor degrees of hyperthyroidism lead to adverse effects in various tissues, even though clinically the patients are euthyroid. To determine whether these anomalies in thyroid function have deleterious effects on renal function and electrolyte metabolism, the plasma concentrations of electrolytes, urea, and creatinine, the renal handling of water and sodium, and the urinary excretion of these substances were measured in patients with nodular goiter who were displaying stable subclinical hyperthyroidism. The studies were carried out before and after correcting the thyroid dysfunction. Restoration of euthyroidism did not modify any of the renal function parameters studied and did not cause changes in blood analyte levels. The data show that treatment of minor degrees of hyperthyroidism does not have any effects on renal function and electrolyte metabolism, and confirm the well-known capacity of the kidney to adjust its functions to changes induced by an abnormal secretion of thyroid hormones.Abbreviations TSH thyrotropin - BW body weight - IV intravenous - Cl chloride - Na sodium - K potassium - GFR glomerular filtration rate - FENa fractional excretion of sodium - T₃ triiodothyronine - T₄ thyroxine - FT₄ free thyroxine - RIA radioimmunoassay - C_NA clearance of sodium - C_H2O clearance of water - C_Osm osmolar clearance