HYPOTHYROIDISM IN A DOG ASSOCIATED WITH TRIMETHOPRIM-SULFADIAZINE THERAPY

Hypothyroidism and a neuromuscular disorder developed in a 4-year-old Golden Retriever after it received potentiated sulphonamide and metron idazole for 18 and 14 weeks, respectively. Serum total T4 concentratio ns were non-detectable before and 6 h after exogenous administration o f 4IU bovine thyroid-stimulating hormone. Thyroid gland biopsy reveale d changes consistent with diffuse hyperplastic goitre. Serum T4 concen trations were normal 7 days after discontinuation of therapy. The long -term trimethoprim-sulphadiazine therapy was considered the most likel y cause of this dog's hyperplastic goitre. The cause of the neuromuscu lar disorder was not determined. It is recommended that discontinuatio n of potentiated sulphonamide takes place at least 7 days prior to any assessment of thyroid function.