Effect of recombinant human thyroid stimulating hormone on radioactive iodine uptake by thyroid carcinoma in dogs.

Abstract

BACKGROUND: The high doses of radioiodine-131 (I) and, subsequently, the high radioactive burden for dog and environment warrants optimization ofI therapy in dogs with thyroid carcinoma (TC). HYPOTHESIS/OBJECTIVES: To evaluate the effect of a revised protocol with recombinant human thyroid stimulating hormone (rhTSH) on tumor radioactive iodine uptake (RAIU) in dogs with TC. ANIMALS: Nine client-owned dogs diagnosed with TC. METHODS: A prospective cross-over study in which tumor RAIU was calculated and compared at 8&#x2009;hours (8h-RAIU) and 24&#x2009;hours (24h-RAIU) after injection of radioactive iodine-123 (I), once with and once without rhTSH (ie, 250&#x2009;&#x3bc;g, IM, 24 and 12&#x2009;hours beforeI) in each dog. Simultaneously, serum total thyroxine (TT4) and TSH were measured at baseline (T), and 6 (T), 12 (T), 24 (T), and 48&#x2009;hours (T) after the first rhTSH administration. RESULTS: Tumor RAIU was significantly higher at 24&#x2009;hours with rhTSH compared to no rhTSH (mean difference&#x2009;=&#x2009;8.85%, 95% CI of [1.56; 16.14]; P&#x2009;=&#x2009;.03), while this was non-significant at 8&#x2009;hours (mean difference&#x2009;=&#x2009;4.54%, 95% CI of [0.35; 8.73]; P&#x2009;=&#x2009;.05). A significant change of serum TT4 (median difference T&#x2009;-&#x2009;T&#x2009;=&#x2009;35.86&#x2009;nmol/L, interquartile range [IQR]&#x2009;=&#x2009;15.74&#x2009;nmol/L) and TSH (median difference T&#x2009;-&#x2009;T&#x2009;=&#x2009;1.20&#x2009;ng/mL, IQR&#x2009;=&#x2009;1.55&#x2009;ng/mL) concentrations occurred after administration of rhTSH (P&#x2009;<&#x2009;.001). CONCLUSIONS AND CLINICAL IMPORTANCE: Recombinant human TSH could optimizeI treatment in dogs with TC by increasing tumor RAIU and thusI treatment efficacy.