New Paper Published in Animals
Thyroid Scintigraphy Findings in 234 Hyperthyroid Cats Before and After Radioiodine Treatment
Summary:
Thyroid scintigraphy is an important tool for diagnosing and staging hyperthyroidism in cats, but it has not been evaluated for treatment success after radioiodine. In a study of 234 hyperthyroid cats, thyroid scans were performed before and six months after treatment. Based on thyroid blood tests, 165 cats (70.5%) returned to normal thyroid function, 54 cats (23.1%) had mild thyroid underactivity (subclinical hypothyroidism), and 15 cats (6.4%) developed more severe hypothyroidism. With follow-up scintigraphy, all cats showed a reduction in the size and activity of the overactive (“hot”) thyroid tumor tissue. In cats with one-sided thyroid disease, the opposite thyroid lobe regained function in 60 of 99 cats (61%). In cats with both thyroid lobes affected, 108 of 135 (80%) maintained thyroid function in both lobes. Persistent “hot” nodules occurred in 26 (11%) cats, but all had normal thyroid function. In contrast, 24 cats (10.4%) had little to no remaining thyroid tissue on follow-up scans, and most of these cats (17/24) had become hypothyroid. Although thyroid scans can help monitor the effectiveness of treatment and confirm destruction of the cat’s thyroid tumor, their ability to distinguish between normal and mildly underactive thyroid function is limited.
