Effects of Levothyroxine Administration and Withdrawal on the Hypothalamic-Pituitary-Thyroid Axis in Euthyroid Dogs
| Autor: | David L. Panciera, V. Ziglioli, William E. Monroe, Katie M. Boes, Gregory C. Troy, Kent R. Refsal |
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| Rok vydání: | 2017 |
| Předmět: |
Male
0301 basic medicine endocrine system medicine.medical_specialty endocrine system diseases 040301 veterinary sciences Levothyroxine Thyrotropin Standard Article Thyroid function tests Canine 0403 veterinary science 03 medical and health sciences Dogs Endocrinology Blood serum Hypothyroidism Thyroid-stimulating hormone Internal medicine medicine Animals Euthyroid Dog Diseases Prospective Studies Triiodothyronine General Veterinary medicine.diagnostic_test business.industry Thyroid 04 agricultural and veterinary sciences Standard Articles Thyroxine Treatment Outcome 030104 developmental biology medicine.anatomical_structure Female SMALL ANIMAL Thyroid function business hormones hormone substitutes and hormone antagonists medicine.drug |
| Zdroj: | Journal of Veterinary Internal Medicine |
| ISSN: | 0891-6640 |
| Popis: | 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 (T4), free thyroxine (fT 4) by equilibrium dialysis, thyroid stimulating hormone; thyrotropin (TSH), and 3,5,3′‐triiodothyronine (T3) were measured every 4 weeks during supplementation and for 16 weeks after levothyroxine was discontinued. Results Mean serum concentrations of T4 and fT 4 were significantly higher (P < .0001) and TSH was lower (P < .0001) in all dogs during levothyroxine administration compared to baseline. Mean serum concentrations of T4, fT 4, and 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. |
| Databáze: | OpenAIRE |
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