Effect of treatment of hyperthyroidism on renal function in cats

Stephen P. DiBartola From the Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210 (DiBartola); Veterinary Nuclear Imaging Center, 34 Creer Rd, Irvine, CA 92714 (Broome); Chicago Cat Clinic, 5301 W Devon Ave, Chicago, IL 60646 (Stein); and Cats Only Veterinary Clinic, 2578 Burrard St, Vancouver, British Columbia, Canada V6J3J7 (Nixon).

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Michael R. Broome From the Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210 (DiBartola); Veterinary Nuclear Imaging Center, 34 Creer Rd, Irvine, CA 92714 (Broome); Chicago Cat Clinic, 5301 W Devon Ave, Chicago, IL 60646 (Stein); and Cats Only Veterinary Clinic, 2578 Burrard St, Vancouver, British Columbia, Canada V6J3J7 (Nixon).

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Barbara S. Stein From the Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210 (DiBartola); Veterinary Nuclear Imaging Center, 34 Creer Rd, Irvine, CA 92714 (Broome); Chicago Cat Clinic, 5301 W Devon Ave, Chicago, IL 60646 (Stein); and Cats Only Veterinary Clinic, 2578 Burrard St, Vancouver, British Columbia, Canada V6J3J7 (Nixon).

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Margie Nixon From the Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210 (DiBartola); Veterinary Nuclear Imaging Center, 34 Creer Rd, Irvine, CA 92714 (Broome); Chicago Cat Clinic, 5301 W Devon Ave, Chicago, IL 60646 (Stein); and Cats Only Veterinary Clinic, 2578 Burrard St, Vancouver, British Columbia, Canada V6J3J7 (Nixon).

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Objective

To determine whether increases in BUN and serum creatinine (SCr) concentrations, which have been reported to develop after surgical bilateral thyroidectomy in hyperthyroid cats, also develop after treatment of hyperthyroidism with radioactive iodine and methimazole.

Design

Prospective, clinical trial.

Animals

58 hyperthyroid cats.

Procedure

Urine specific gravity, SCr, BUN, and serum thyroxine (T4) concentrations were determined before and 30 and 90 days after treatment of hyperthyroidism with radioactive iodine, methimazole, or surgical bilateral thyroidectomy.

Results

Mean SCr and BUN concentrations determined 30 and 90 days after treatment were significantly higher than those measured before treatment. Mean SCr, BUN, and T4 concentrations were not different among groups before treatment or 30 and 90 days after treatment.

Clinical Implications

Reduction of serum T4 concentrations after treatment of hyperthyroidism may result in azotemia in older cats with chronic renal disease. Treating azotemic hyperthyroid cats with methimazole until it can be determined whether correction of the hyperthyroid state will exacerbate the azotemia may be prudent. (J Am Vet Med Assoc 1996;208:875–878)

Objective

To determine whether increases in BUN and serum creatinine (SCr) concentrations, which have been reported to develop after surgical bilateral thyroidectomy in hyperthyroid cats, also develop after treatment of hyperthyroidism with radioactive iodine and methimazole.

Design

Prospective, clinical trial.

Animals

58 hyperthyroid cats.

Procedure

Urine specific gravity, SCr, BUN, and serum thyroxine (T4) concentrations were determined before and 30 and 90 days after treatment of hyperthyroidism with radioactive iodine, methimazole, or surgical bilateral thyroidectomy.

Results

Mean SCr and BUN concentrations determined 30 and 90 days after treatment were significantly higher than those measured before treatment. Mean SCr, BUN, and T4 concentrations were not different among groups before treatment or 30 and 90 days after treatment.

Clinical Implications

Reduction of serum T4 concentrations after treatment of hyperthyroidism may result in azotemia in older cats with chronic renal disease. Treating azotemic hyperthyroid cats with methimazole until it can be determined whether correction of the hyperthyroid state will exacerbate the azotemia may be prudent. (J Am Vet Med Assoc 1996;208:875–878)

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