J Am Vet Med Assoc, 2005. 227(1): p.32.
I read with initial astonishment Nykamp et al’s recent report (JAVMA, May 15, 2005, pp 1671–1675) of a 30.3% incidence of posttreatment hypothyroidism among hyperthyroid cats treated with iodine 131 (131I). Such outcomes are at odds with my experience. In 23 years of practice, I have not diagnosed hypothyroidism in a single cat, either from naturally occurring disease or following 131I treatment. Reading further, I found the authors were diagnosing hypothyroidism on the basis of total serum thyroxine (T4) concentrations alone, not on the presence of clinical signs of disease.