Effect of a Limited Iodine Diet on Iodine Uptake by Thyroid Glands in Hyperthyroid Cats

摘要

AbstractBackgroundThe effect of feeding a limited iodine diet on radioactive iodine uptake in the thyroid glands of hyperthyroid cats is unknown.ObjectivesTo determine how feeding limited dietary iodine affects radioactive iodine uptake by the thyroid glands of hyperthyroid cats.AnimalsEight geriatric cats with spontaneous hyperthyroidism.MethodsProspective study of eight client owned hyperthyroid cats fed a commercially available iodine limited diet for 6 months. Clinical signs were evaluated and TT4 and fT4 were measured during consumption of the diet. Uptake of 123I was determined before and 8–16 weeks after exclusive consumption of the diet.ResultsClinical signs of hyperthyroidism resolved in all cats, but there was no significant increase in body weight. TT4 and fT4 decreased into the reference range by 8–16 weeks in all cats. Mean TT4 before consumption of the diet was 9.7 μg/dL (SD 5.2) and after consumption of the diet was 3.1 μg/dL (SD 0.9). Scintigraphy revealed unilateral uptake of isotope in 5 cats and bilateral uptake in 3 cats. Mean percentage uptake of 123I by the thyroid gland at 8 hours after isotope administration was 16.2 (SD 11.8) before diet consumption and 34.6 (SD 11.7) 8–16 weeks after exclusive consumption of the diet. The percentage increase was variable between cats (38–639%).Conclusions and clinical importanceLimited iodine diets increase iodine uptake in the autonomous thyroid glands of hyperthyroid cats. Further studies are necessary to determine if consumption of a limited iodine diet changes sensitivity of the thyroid gland to 131I treatment.