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Hyperthyroidism
Endocrine and MetabolicAll SpeciesNew
Key Points
  • Hyperthyroidism is an endocrinopathy caused by excess production of thyroid hormones (T3 and T4)
    • It is the most common endocrinopathy in older cats
  • Typically caused by a functional adenoma in one or both of the thyroid lobes
  • The classic presentation includes weight loss despite an increased appetite, hyperactivity, a palpable thyroid slip and polyuria / polydipsia
  • Diagnosis is based on thyroid hormone testing with total T4 used first-line and free T4 as a confirmatory test
  • The main treatment options are radioactive iodine, surgical removal of the thyroid nodule, medical management and dietary iodine restriction
    • Radioactive iodine is generally the best definitive treatment in most cats
  • Once treatment is started, cats must be monitored carefully for unmasked renal disease, adverse drug reactions and iatrogenic hypothyroidism
Differential Diagnoses
  1. Chronic kidney disease
  2. Diabetes mellitus
  3. Chronic inflammatory enteropathies (CIE)
  4. Intestinal lymphoma
  5. Hypertrophic cardiomyopathy (HCM)
Overview
Aetiology
Clinical Signs
Diagnosis
Treatment
Prevention
Resources
Overview

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Aetiology

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Clinical Signs

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Diagnosis

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Treatment

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Prevention

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Resources

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Educational content only. This factsheet is for general veterinary education and is not a substitute for professional veterinary advice, diagnosis, or treatment. Not for use in an emergency — contact a veterinarian or emergency service. Full disclaimer →