EFFECT OF TREATMENT OF HYPERTHYROIDISM ON RENAL-FUNCTION IN CATS

Objective-To determine whether increases in BUN and serum creatinine ( SCr) concentrations, which have been reported to develop after surgica l bilateral thyroidectomy in hyperthyroid cats, also develop after tre atment of hyperthyroidism with radioactive iodine and methimazole. Des ign-Prospective, clinical trial. Animals-58 hyperthyroid cats. Procedu re-Urine specific gravity, SCr, BUN, and serum thyroxine (T-4) concent rations were determined before and 30 and 90 days after treatment of h yperthyroidism with radioactive iodine, methimazole, or surgical bilat eral thyroidectomy. Results-Mean SCr and BUN concentrations determined 30 and 90 days alter treatment were significantly higher than those m easured before treatment. Mean SCr, BUN, and T-4 concentrations were n ot different among groups before treatment or 30 and 90 days after tre atment. Clinical Implications-Reduction of serum T-4 concentrations af ter treatment of hyperthyroidism may result in azotemia in older cats with chronic renal disease. Treating azotemic hyperthyroid cats with m ethimazole until it can be determined whether correction of the hypert hyroid state will exacerbate the azotemia may be prudent.