Peer-reviewed veterinary case report
Total thyroxine (TT4) levels and outliers in 531,765 US cats 2014-2015
By Lottati, Maya et al.·Published in PloS one·2019·VCA Veterinary Specialists of the Valley- Department of Internal Medicine, United States·View original on PubMed →
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Original publication title: Expected total thyroxine (TT4) concentrations and outlier values in 531,765 cats in the United States (2014-2015).
- Species:
- cat
Plain-English summary
A study looked at thyroid hormone levels in over 531,000 cats to help identify hyperthyroidism, a common condition in older cats. It found that cats with total thyroxine (TT4) levels above 3.5 micrograms per deciliter are considered outliers and may need further evaluation for hyperthyroidism. The research also showed that the likelihood of having elevated TT4 levels increases significantly as cats age, especially between 7 and 14 years. This information can help veterinarians catch hyperthyroidism earlier in older cats, leading to better management of the condition.
People also search for: cat hyperthyroidism symptoms · elevated TT4 levels in cats · older cat thyroid problems
Abstract
BACKGROUND: Levels exceeding the standard reference interval (RI) for total thyroxine (TT4) concentrations are diagnostic for hyperthyroidism, however some hyperthyroid cats have TT4 values within the RI. Determining outlier TT4 concentrations should aid practitioners in identification of hyperthyroidism. The objective of this study was to determine the expected distribution of TT4 concentration using a large population of cats (531,765) of unknown health status to identify unexpected TT4 concentrations (outlier), and determine whether this concentration changes with age. METHODOLOGY/PRINCIPLE FINDINGS: This study is a population-based, retrospective study evaluating an electronic database of laboratory results to identify unique TT4 measurement between January 2014 and July 2015. An expected distribution of TT4 concentrations was determined using a large population of cats (531,765) of unknown health status, and this in turn was used to identify unexpected TT4 concentrations (outlier) and determine whether this concentration changes with age. All cats between the age of 1 and 9 years (n = 141,294) had the same expected distribution of TT4 concentration (0.5-3.5ug/dL), and cats with a TT4 value >3.5ug/dL were determined to be unexpected outliers. There was a steep and progressive rise in both the total number and percentage of statistical outliers in the feline population as a function of age. The greatest acceleration in the percentage of outliers occurred between the age of 7 and 14 years, which was up to 4.6 times the rate seen between the age of 3 and 7 years. CONCLUSIONS: TT4 concentrations >3.5ug/dL represent outliers from the expected distribution of TT4 concentration. Furthermore, age has a strong influence on the proportion of cats. These findings suggest that patients with TT4 concentrations >3.5ug/dL should be more closely evaluated for hyperthyroidism, particularly between the ages of 7 and 14 years. This finding may aid clinicians in earlier identification of hyperthyroidism in at-risk patients.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/30840691/