2016 ACVIM Forum Research Abstract Program

In this small group of cats, pre-treatment with a limited iodine diet did not adversely affect the response to 131-I therapy. Many dogs are misdiagnosed with hypothyroidism because of the vague presenting signs and limitations of thyroid function tests, leading to inappropriate treatment with levothyroxine. During chronic supplementation, the hypothalamic-pituitary-thyroid axis (HPTA) is suppressed and may make it difficult to accurately determine thyroid function following withdrawal of levothyroxine. We sought to determine if the HPTA is suppressed following levothyroxine administration in euthyroid dogs and the time required for resolution of any suppression. We hypothesized that levothyroxine administration would suppress the HPTA in euthyroid dogs and that the HPTA would recover within 8 weeks in all dogs, regardless of the duration of treatment.