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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.

Several drugs are known to cause artificially low thyroxine (T4) concentrations in the blood, and so can confuse the diagnosis of hypothyroidism

The following is an alphabetical list of some of the drugs that are known to reduce the concentration of thyroxine (T4) in blood samples :

  • Androgens
  • Diazepam
  • Glucocorticoids
  • Iodine
  • Mitotane
  • Penicillin
  • Phenobarbitone
  • Phenylbutazone
  • Phenytoin
  • Primidone
  • Propylthiouracil
  • Salicylates
  • Sulphonylureas
  • Thyroxine (T4)*
  • Triiodothyronine (T3)*

* Due to temporary suppression of TSH. Treatment with T3 or T4 should be discontinued for at least 2 months before estimating basal T4 concentrations.

A Thyroid Stimulating Hormone stimulation test should be performed to distinguish between drug suppression and true hypothyroidism.


Last updated : October 2013