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This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Euthyroid Sick Syndrome is the term given to abnormally low thyroxine (T4) concentrations in the blood, even though thyroid function is actually normal. For this reason a diagnosis of hypothyroidism should be confirmed by performing a Thyroid Stimulating Hormone stimulation test, and should not be based on low basal T4 concentrations alone.

The precise mechanism that leads to abnormally low thyroxine (T4) concentrations in the blood are not fully understood, but it may be associated with low circulating protein concentrations or reduced binding of T4 to blood proteins. In any event the following is an alphabetical list of some of the clinical conditions which can cause a low T4 even though thyroid function is normal :

  • Autoimmune hemolyticanaemia
  • Cardiomyopathy
  • Diabetes mellitus
  • Generalised skin disease (eg demodex)
  • Heart failure (congestive)
  • Hepatitis (chronic active)
  • Infections
  • Intervertebral disc protrusion
  • Liver failure (eg cirrhosis)
  • Lymphosarcoma
  • Malabsorption
  • Megaoesophagus
  • Nephrotic syndrome
  • Polyneuropathy
  • Protein-losing enteropathy
  • Renal failure (chronic)
  • Starvation
  • Systemic lupus erythematosus (SLE)

Last updated : October 2013