Iodine Content as Contributor to Feline Hyperthyroidism

Clinician's Brief (Capsule)

First described in 1979, feline hyperthyroidism has become an increasingly common endocrinopathy of geriatric cats, and concentration of iodine in commercial foods may be a contributing factor.

Multiple cat-food brands (112 over-the-counter and prescription diets) from 3 geographic regions (ie, west coast, Florida, Midwest) were purchased and iodine concentration measured. Seventy-one were canned, 19 were pouched, and 22 were dry foods. Eight brands and 2 supermarket varieties were tested. The daily iodine intake for a hypothetical 4.5-kg cat or 1.4-kg kitten was calculated based on manufacturer feeding instructions. Although no significant difference was found in iodine concentration across the 3 regions, variations were noted across packaging types, brands, seafood ingredients, and intended use (ie, therapeutic or not). Canned foods showed the greatest variation, in which an intake between 49 and 9,639 µg iodine/day was calculated.

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