Feline Hyperthyroidism (fT4)
Feline hyperthyroidism is a common endocrine disease of older cats caused by excessive thyroid hormone production. Total thyroxine (fT4) is a primary screening aid; quantitative measurement supports diagnosis and subsequent monitoring of therapy. Point-of-care testing returns an objective fT4 concentration that can be combined with clinical signs and age-appropriate reference ranges.
Fact Table
| Species | Feline |
|---|---|
| Biomarkers | Feline Total Thyroxine (fT4) |
| Tests |
Clinical Context
Feline hyperthyroidism is a common endocrine disease of older cats caused by excessive thyroid hormone production. Total thyroxine (fT4) is a primary screening aid; quantitative measurement supports diagnosis and subsequent monitoring of therapy. Point-of-care testing returns an objective fT4 concentration that can be combined with clinical signs and age-appropriate reference ranges.
Interpretation should combine the quantitative result with the patient's signalment, history, clinical signs, vaccination or treatment history where relevant, and any other laboratory findings. A single value is rarely diagnostic on its own; serial measurements often provide more useful information.
Related Biomarkers
Related Test Kits
Related Articles
- Feline Hyperthyroidism: The T4 Test and Its Misses Hyperthyroidism is the most common endocrine disease of older cats, but early disease and concurrent illness can leave T4 normal. Here's the grey zone.
- Thyroid Testing in Dogs and Cats: T4 and TSH Explained A guide to thyroid testing in dogs and cats: total T4 and TSH ranges, hyperthyroidism in cats, hypothyroidism in dogs, and monitoring.
Clinical literature cited in related articles
2026-09-12
MEDIUM
FAQ
What does a feline thyroid test measure?
It measures total thyroxine (T4) and, when needed, thyroid-stimulating hormone (TSH) in serum or plasma to assess thyroid function. High T4 is diagnostic of hyperthyroidism, the most common endocrine disease of older cats.
What symptoms suggest thyroid problems in cats?
Hyperthyroidism typically causes weight loss despite a ravenous appetite, hyperactivity, vomiting, and a rapid heart rate. These signs in a middle-aged or older cat should prompt thyroid testing.
How is the test performed?
A blood sample is collected and T4 (and TSH) measured quantitatively on an immunofluorescence analyzer. Precise concentrations with age-appropriate reference ranges support diagnosis and subsequent monitoring of therapy.