#53-S dietary and environmental risk factors for clinical hyperthyroidism in pet cats

PURPOSE: The prevalence of hyperthyroidism in pet cats (benign nodular hyperplasia) has reached epidemic proportions, since it was first described in 1979. Therefore, we tested the hypothesis that consumption of canned foods compared with dry foods increases the risk of hyperthyroidism. Furthermore, the risk associated with lower iodine concentrations in canned foods and chemicals in can linings was evaluated. Secondary hypotheses were that hyperthyroid risk is increased by well water consumption and exposure to environmental endocrine disrupters. METHODS: Case cats (n = 109) had serum T4 concentration greater-or-equal, slanted5.0 μg/dl and greater-or-equal, slanted1 clinical sign of hyperthyroidism; control cats (n = 173) had a serum T4 concentration less-than-or-equals, slant3.5 μg/dl. RESULTS: Lifetime canned (vs. dry) food consumption was associated with increased risk (greater-or-equal, slanted50% canned: OR = 3.45, 95% CI: 1.77, 6.74; <50% canned: OR = 2.84, 95% CI: 1.48, 5.46). Other significant risk factors were use of cans with easy-open lids (vs. dry) (OR = 3.79, 95% CI: 1.68, 8.54), foods without iodine supplementation in any life stage (OR = 4.09, 95% CI: 1.09, 15.40), years of well water consumption (OR = 1.12, 95% CI: 1.02, 1.23), years of exposure to gas fireplaces (OR = 1.16, 95% CI: 1.02, 1.31), age (OR = 1.15, 95% CI: 1.03, 1.29), and female gender (OR = 2.73, 95% CI: 1.38, 5.43). CONCLUSIONS: Endocrine disrupters in food can linings and the environment may explain the recent epidemic of hyperthyroidism in cats, since easy-open cans have gained popularity. This same relationship should also be evaluated in humans.