Minnesota Journal of Veterinary Medicine, 1987. 27: p.28-32.
Twenty-three hyperthyroid cats were treated with a fixed 5 mCi dose of I-131. In 19 cats, serum thyroxine concentrations were normal following therapy (serum thyroxine concentration = 1.0 to 4 ug/dl); and remained normal during the followup period. Serum thyroxine concentration remained greater than 4 ug/dl in 2 cats and was less than 1.0 ug/dl in two cats. One cat died 48 hours following I-131 therapy, The use of I-131 appears to safe and effective treatment for feline hyperthyroidism. The present study suggests that a fixed close of I-131 is as effective as calculated dosages based on thyroid weight, radioiodine half-life and radioiodine uptake by the thyroid gland.