Thyroid Scintigraphy Findings in 234 Hyperthyroid Cats Before and After Radioiodine Treatment
Thyroid scintigraphy is a key tool for diagnosing and staging hyperthyroidism in cats, but follow-up scintigraphic studies after radioiodine treatment are limited. This multicentric study evaluated <sup>99m</sup>Tc-pertechnetate scintigraphy findings in 234 hyperthyroid cats before and 6...
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2025-05-01
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| author | Lisa Stammeleer Pilar Xifra Sara I. Serrano Eva Vandermeulen Sylvie Daminet Mark E. Peterson |
| author_facet | Lisa Stammeleer Pilar Xifra Sara I. Serrano Eva Vandermeulen Sylvie Daminet Mark E. Peterson |
| author_sort | Lisa Stammeleer |
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| description | Thyroid scintigraphy is a key tool for diagnosing and staging hyperthyroidism in cats, but follow-up scintigraphic studies after radioiodine treatment are limited. This multicentric study evaluated <sup>99m</sup>Tc-pertechnetate scintigraphy findings in 234 hyperthyroid cats before and 6 months after radioiodine treatment. Based on serum T4 and TSH concentrations, 165 (70.5%) became euthyroid, 54 (23.1%) had subclinical hypothyroidism, and 15 (6.4%) developed overt hypothyroidism. On post-treatment scintigraphy, all cats showed reduced size and radionuclide uptake of “hot” thyroid nodules. Of 99 cats with unilateral nodules, 60 (61%) recovered function in the contralateral lobe. Among 135 cats with bilateral nodules, both lobes remained visible in 108 (80%). Persistent “hot” nodules with high thyroid/salivary (T/S) ratios or thyroidal pertechnetate uptake (TcTU) occurred in 26 (11%) cats, all of which were euthyroid. Conversely, 24 (10.4%) cats had minimal or absent thyroid tissue with 17 (71%) being hypothyroid, but seven (29%) were euthyroid. As a diagnostic test for iatrogenic hypothyroidism, TcTU showed the highest sensitivity (62.3), with the T/S ratio (7.3) and background-corrected T/S ratio (30.4) being much lower (<i>p</i> < 0.01). While follow-up scintigraphy aids in assessing thyroid tumor destruction and residual function, its diagnostic utility for differentiating euthyroidism and hypothyroidism is limited, especially for cats with mild (subclinical) hypothyroidism. |
| format | Article |
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| publishDate | 2025-05-01 |
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| series | Animals |
| spelling | doaj-art-e80740f46523479cb0237b0f26268c612025-08-20T01:57:04ZengMDPI AGAnimals2076-26152025-05-011510149510.3390/ani15101495Thyroid Scintigraphy Findings in 234 Hyperthyroid Cats Before and After Radioiodine TreatmentLisa Stammeleer0Pilar Xifra1Sara I. Serrano2Eva Vandermeulen3Sylvie Daminet4Mark E. Peterson5Small Animal Department, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, BelgiumIodocat, Leganés, 28919 Madrid, SpainIodocat, Leganés, 28919 Madrid, SpainDepartment of Medical Imaging of Domestic Animals, Ghent University, 9820 Merelbeke, BelgiumSmall Animal Department, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, BelgiumAnimal Endocrine Clinic, New York, NY 10025, USAThyroid scintigraphy is a key tool for diagnosing and staging hyperthyroidism in cats, but follow-up scintigraphic studies after radioiodine treatment are limited. This multicentric study evaluated <sup>99m</sup>Tc-pertechnetate scintigraphy findings in 234 hyperthyroid cats before and 6 months after radioiodine treatment. Based on serum T4 and TSH concentrations, 165 (70.5%) became euthyroid, 54 (23.1%) had subclinical hypothyroidism, and 15 (6.4%) developed overt hypothyroidism. On post-treatment scintigraphy, all cats showed reduced size and radionuclide uptake of “hot” thyroid nodules. Of 99 cats with unilateral nodules, 60 (61%) recovered function in the contralateral lobe. Among 135 cats with bilateral nodules, both lobes remained visible in 108 (80%). Persistent “hot” nodules with high thyroid/salivary (T/S) ratios or thyroidal pertechnetate uptake (TcTU) occurred in 26 (11%) cats, all of which were euthyroid. Conversely, 24 (10.4%) cats had minimal or absent thyroid tissue with 17 (71%) being hypothyroid, but seven (29%) were euthyroid. As a diagnostic test for iatrogenic hypothyroidism, TcTU showed the highest sensitivity (62.3), with the T/S ratio (7.3) and background-corrected T/S ratio (30.4) being much lower (<i>p</i> < 0.01). While follow-up scintigraphy aids in assessing thyroid tumor destruction and residual function, its diagnostic utility for differentiating euthyroidism and hypothyroidism is limited, especially for cats with mild (subclinical) hypothyroidism.https://www.mdpi.com/2076-2615/15/10/1495hyperthyroidismhypothyroidism<sup>99m</sup>Tc-pertechnetateradioactive iodine<sup>131</sup>I |
| spellingShingle | Lisa Stammeleer Pilar Xifra Sara I. Serrano Eva Vandermeulen Sylvie Daminet Mark E. Peterson Thyroid Scintigraphy Findings in 234 Hyperthyroid Cats Before and After Radioiodine Treatment Animals hyperthyroidism hypothyroidism <sup>99m</sup>Tc-pertechnetate radioactive iodine <sup>131</sup>I |
| title | Thyroid Scintigraphy Findings in 234 Hyperthyroid Cats Before and After Radioiodine Treatment |
| title_full | Thyroid Scintigraphy Findings in 234 Hyperthyroid Cats Before and After Radioiodine Treatment |
| title_fullStr | Thyroid Scintigraphy Findings in 234 Hyperthyroid Cats Before and After Radioiodine Treatment |
| title_full_unstemmed | Thyroid Scintigraphy Findings in 234 Hyperthyroid Cats Before and After Radioiodine Treatment |
| title_short | Thyroid Scintigraphy Findings in 234 Hyperthyroid Cats Before and After Radioiodine Treatment |
| title_sort | thyroid scintigraphy findings in 234 hyperthyroid cats before and after radioiodine treatment |
| topic | hyperthyroidism hypothyroidism <sup>99m</sup>Tc-pertechnetate radioactive iodine <sup>131</sup>I |
| url | https://www.mdpi.com/2076-2615/15/10/1495 |
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