Peer-reviewed veterinary case report
Thyroid disease gets worse the longer cats have hyperthyroidism
By Peterson, Mark E et al.·Published in Journal of feline medicine and surgery·2016·Animal Endocrine Clinic, United States·View original on PubMed →
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Original publication title: Prevalence and degree of thyroid pathology in hyperthyroid cats increases with disease duration: a cross-sectional analysis of 2096 cats referred for radioiodine therapy.
- Species:
- cat
Plain-English summary
A group of 2,096 cats with hyperthyroidism (an overactive thyroid) was studied to see how the severity of their condition changed over time. The findings showed that as the disease lasted longer, the levels of thyroid hormone (T4) in their blood increased, and the size and number of thyroid tumors also grew. Cats diagnosed for more than four years had a much higher chance of having large or multiple tumors, and some were suspected to have cancer. These results highlight the importance of monitoring hyperthyroidism in cats, as more severe cases develop with time, often requiring treatments like radioiodine therapy.
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Abstract
OBJECTIVES: Hyperthyroidism is common in cats, but there are no reports that evaluate its severity or underlying thyroid tumor disease based on disease duration (ie, time from original diagnosis). The objective of this study was to compare serum thyroxine (T4) concentrations and thyroid scintigraphic characteristics of cats referred for radioiodine treatment based on disease duration. METHODS: This was a cross-sectional study of 2096 cats with hyperthyroidism. Cats were divided into five groups based on time from diagnosis: ⩽1 year (n = 1773); >1-2 years (n = 169); >2-3 years (n = 88); >3-4 years (n = 35); and >4-6.1 years (n = 31). Methimazole, administered to 996 (47.5%) cats, was stopped at least 1 week prior to examination to allow for serum T4 testing. Each thyroid scintiscan was evaluated for pattern (unilateral, bilateral, multifocal), location (cervical, thoracic inlet, chest) and size (small, medium, large, huge) of the thyroid tumor, as well as features suggesting malignancy. RESULTS: Median serum T4 concentration increased with increasing disease duration from 100 nmol/l (⩽1 year) to 315 nmol/l (>4-6.1 years) (P <0.001). Prevalence of unilateral thyroid disease decreased, whereas multifocal disease (three or more tumor nodules) increased (P <0.001) with increasing disease duration. Median tumor volume in the five groups increased from 1.6 cm(3) (⩽1 year) to 6.4 cm(3) (>4-6.1 years). Prevalence of large (4-8 cm(3)) and huge (>8 cm(3)) thyroid tumors increased from 5.1% (⩽1 year) to 88.6% (>4-6.1 years), while the prevalence of intrathoracic tumor tissue increased from 3.4% (⩽1 year) to 32.3% (>4-6.1 years). Prevalence of suspected thyroid carcinoma (characterized by severe hyperthyroidism; huge, intrathoracic, multifocal tumors; refractory to methimazole treatment) increased with increasing disease duration from 0.4% (⩽1 year) to 19.3% (>4-6.1 years). CONCLUSIONS AND RELEVANCE: Our results indicate that the prevalence of severe hyperthyroidism, large thyroid tumors, multifocal disease, intrathoracic thyroid masses and suspected malignant disease all increase with disease duration in cats referred for radioiodine therapy.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/25673019/