Effect of Feeding an Iodine‐Restricted Diet in Cats with Spontaneous Hyperthyroidism

Abstract

BackgroundExclusive feeding of an iodine‐restricted diet has been proposed as a method for controlling clinical manifestations of hyperthyroidism in hyperthyroid cats.ObjectivesTo determine the effect of feeding an iodine‐restricted diet on TT4 concentrations and clinical signs in cats with spontaneous hyperthyroidism.AnimalsForty‐nine client‐owned cats with spontaneous hyperthyroidism.MethodsRetrospective case series. Hyperthyroid cats were exclusively fed a commercially available iodine‐restricted diet. Clinical response was assessed by change in weight and heart rate and serum TT4, blood urea nitrogen (BUN), and creatinine concentrations at various times during dietary management (21–60 days, 60–180 days).ResultsSerum TT4 normalized in 20/48 cats (42%) and 39/47 cats (83%) at 21–60 days and 61–180 days, respectively. Cats in which the TT4 concentrations were still above reference range at 21–60 days had a significantly higher starting TT4 than those that normalized their TT4 levels during the same time period (P = .038). Body weight did not significantly increase (P = .34) nor heart rate decrease (P = .64) during the study. There was a significant decrease in serum creatinine (P = .028). Cats in the low reference range for serum TT4 concentrations did not have a significant increase in body weight (P = .41) nor creatinine (P = .54) when compared to those with high reference range.Conclusions and Clinical ImportanceRestricted‐iodine diets were effective at maintaining serum TT4 concentrations within reference ranges for a majority of cats with spontaneous hyperthyroidism over 1 year, although not all clinical signs of hyperthyroidism improved.

Iodine-restricted food versus pharmacological therapy in the management of feline hyperthyroidism: A controlled trial in 34 cats

“…It has been observed that treatment of feline hyperthyroidism with methimazole results in a decrease in glomerular filtration rate and an increase in serum creatinine concentrations (Graves et al, 1994;Becker et al, 2000). On the contrary, the authors of both previous studies on the treatment of feline hyperthyroidism with an iodine-restricted food reported no changes in serum creatinine concentrations (Van der Kooij et al, 2014;Hui et al, 2015). Our study confirms these data.…”

“…Nevertheless, in the only long-term follow-up study performed with hyperthyroid cats, an initial weight gain has been described (Boretti et al, 2014). The lack of increase in body weight is also reported in cats treated with iodine-restricted food (Hui et al, 2015). In our study, despite the lowering of serum TT 4 in all groups, no significant variations were found in body weight.…”

“…Although this was not a primary goal of the present study, only median TT 4 concentrations of methimazole groups have reached this objective after 3 months of treatment. Until now, there are only two published studies regarding the use of iodine-restricted food in clientowned hyperthyroid cats (Van der Kooij et al, 2014;Hui et al, 2015). Our results on the ability of the iodinerestricted food to normalize the TT 4 concentration (37.5% of cats with serum TT 4 concentration within reference range 60 days after starting treatment) were similar to those observed by Hui et al (2015) (42% of cats with serum TT 4 concentration within reference range 21-60 days after starting treatment) but lower than those reported by van der Kooij et al (2014) (75% of cats with serum TT 4 concentration within reference range after 8 weeks).…”

“…Recently, dietary treatment of feline hyperthyroidism has been proposed. At present, only two studies have been published about the administration of an iodinerestricted food as therapy in client-owned hyperthyroid cats and neither was a controlled study (Van der Kooij et al, 2014;Hui et al, 2015). The aim of the present study was to evaluate the effects of an iodine-restricted food on clinical and clinicopathological parameters in client-owned cats with hyperthyroidism and to compare the efficacy of dietetic treatment with that of standard pharmacological therapy with oral and transdermal methimazole.…”

Double‐blinded randomised placebo‐controlled clinical trial of individualised homeopathic treatment of hyperthyroid cats

“…Iodine-restricted food was unpalatable in approximately 75 per cent of 225 hyperthyroid cats (van der Kooij and others 2014), while the suitability of such a diet for the lifelong feeding of older cats is questioned (Peterson 2012b). A more recent retrospective study of 49 hyperthyroid cats maintained on an iodine-restricted diet failed to show statistically significant changes in either heart rate or weight for the 39/47 (83 per cent) that became euthyroid over a 180-day period (Hui and others 2015). Bilateral thyroidectomy can result in hypoparathyroidism with life-threatening hypocalcaemia a potential sequel (Naan and others 2006).…”