Peer-reviewed veterinary case report
How levothyroxine affects thyroid tests in healthy dogs
By Ziglioli, V et al.·Published in Journal of veterinary internal medicine·2017·Department of Small Animal Clinical Sciences·View original on PubMed →
PetCaseFinder translated the abstract of this peer-reviewed paper into plain English so pet owners can read it. We do not publish original research — every detail traces back to the citation above. How we work →
Original publication title: Effects of Levothyroxine Administration and Withdrawal on the Hypothalamic-Pituitary-Thyroid Axis in Euthyroid Dogs.
- Species:
- dog
Plain-English summary
A group of healthy dogs receiving levothyroxine, a medication for thyroid issues, showed changes in their thyroid hormone levels during treatment. After stopping the medication, it took about a week for their thyroid function tests to return to normal. This means that if your dog has been on levothyroxine, it’s important to wait a week after stopping the medication before checking their thyroid levels to get an accurate reading.
People also search for: dog thyroid medication side effects · levothyroxine for dogs · how long to wait after stopping levothyroxine for thyroid test
Abstract
BACKGROUND: Chronic supplementation can suppress the hypothalamic-pituitary-thyroid axis (HPTA) and make it difficult to assess thyroid function after withdrawal of levothyroxine. OBJECTIVES: To determine whether the HPTA is suppressed after levothyroxine administration in euthyroid dogs and the time required for resolution of any suppression. ANIMALS: Twenty-eight healthy euthyroid dogs. METHODS: A prospective, randomized study administering levothyroxine to euthyroid dogs for 8 weeks (group 1) or 16 weeks (group 2). Serum concentrations of total thyroxine (T), free thyroxine (fT) by equilibrium dialysis, thyroid stimulating hormone; thyrotropin (TSH), and 3,5,3'-triiodothyronine (T) were measured every 4 weeks during supplementation and for 16 weeks after levothyroxine was discontinued. RESULTS: Mean serum concentrations of Tand fTwere significantly higher (P < .0001) and TSH was lower (P < .0001) in all dogs during levothyroxine administration compared to baseline. Mean serum concentrations of T, fTand TSH in both groups, beginning 1 week after levothyroxine was discontinued, were significantly different (P < .01) compared to values during levothyroxine administration but not compared to baseline values (P > .3). CONCLUSIONS AND CLINICAL IMPORTANCE: Assessing thyroid function tests 1 week after cessation of levothyroxine at 26 μg/kg once a day for up to 16 weeks will provide an accurate assessment of thyroid function in healthy euthyroid dogs.
Find similar cases for your pet
PetCaseFinder finds other peer-reviewed reports of pets with the same symptoms, plus a plain-English summary of what was tried across them.
Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/28432797/