Do subtherapeutic dosages of levothyroxine harm euthyroid dogs?
Thyroid supplementation is not indicated in a euthyroid dog, said Dr. Panciera, but as long as high doses that induce hyperthyroidism are avoided, he doubts that it is harmful. A dog may become temporarily hypothyroid when treatment is withdrawn. • Can therapy be adjusted based on post-treatment TSH concentrations? Although this has not been critically evaluated, Dr. Refsal believes that TSH concentrations decrease once post-pill T4 concentrations are normal to high (the TSH assay does not identify low TSH values, however). Dr. Scott-Moncrieff studied TSH concentrations over a 12-hour period after administering sodium levothyroxine and found no significant change. Dr. Ferguson commented that TSH concentration was within the normal range in a group of dogs treated with standard, twice daily therapy.
