Peer-reviewed veterinary case report
Thyroid hormone tests and TSH stimulation in radioiodine-treated cats
By Wakeling, Jennifer et al.·Published in Journal of veterinary internal medicine·2020·Douglas College, Canada·View original on PubMed →
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Original publication title: Correlation of thyroid hormone measurements with thyroid stimulating hormone stimulation test results in radioiodine-treated cats.
- Species:
- cat
Plain-English summary
A group of cats that had been treated for hyperthyroidism with radioiodine (RAI) were tested for thyroid hormone levels to check for iatrogenic hypothyroidism, a condition that can occur after treatment. The study found that many of the cats with low thyroid hormone levels also had high thyroid-stimulating hormone (TSH) levels, indicating hypothyroidism. However, noncritical illness did not significantly affect the test results. The findings suggest that specific blood tests can help veterinarians diagnose this condition in cats effectively.
People also search for: cat thyroid problems after radioiodine treatment · hypothyroidism symptoms in cats · cat TSH test results interpretation
Abstract
BACKGROUND: Iatrogenic hypothyroidism can develop after radioiodine-I(RAI) treatment of hyperthyroid cats and can be diagnosed using the thyroid stimulating hormone (TSH) stimulation test. OBJECTIVES: To assess the effect of noncritical illness on TSH stimulation test results in euthyroid and RAI-treated cats. To assess the correlation of low total-thyroxine (tT4), low free-thyroxine (fT4), and high TSH concentrations with TSH stimulation test results. ANIMALS: Thirty-three euthyroid adult cats and 118 client-owned cats previously treated with RAI. METHODS: Total-thyroxine, fT4, and TSH were measured, and a TSH stimulation test was performed in all cats. Euthyroid control cats were divided into apparently healthy and noncritical illness groups. RAI-treated cats were divided into RAI-hypothyroid (after-stimulation tT4 ≤ 1.5 μg/dL), RAI-euthyroid (after-stimulation tT4 ≥ 2.3 μg/dL OR after-stimulation tT4 1.5-2.3 μg/dL and before : after tT4 ratio > 1.5), and RAI-equivocal (after stimulation tT4 1.5-2.3 μg/dL and tT4 ratio < 1.5) groups. RESULTS: Noncritical illness did not significantly affect the tT4 following TSH stimulation in euthyroid (P = .38) or RAI-treated cats (P = .54). There were 21 cats in the RAI-equivocal group. Twenty-two (85%) RAI-hypothyroid cats (n = 26) and 10/71 (14%) of RAI-euthyroid cats had high TSH (≥0.3 ng/mL). Twenty-three (88%) RAI-hypothyroid cats had low fT4 (<0.70 ng/dL). Of the 5 (7%) RAI-euthyroid cats with low fT4, only one also had high TSH. Only 5/26 (19%) RAI-hypothyroid cats had tT4 below the laboratory reference interval (<0.78 μg/dL). CONCLUSIONS AND CLINICAL RELEVANCE: The veterinary-specific chemiluminescent fT4 immunoassay and canine-specific TSH immunoassay can be used to aid in the diagnosis of iatrogenic hypothyroidism in cats.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/33044029/