Abstract
Hypothyroidism is a common endocrine disease in the dog, the main symptoms of this disorder are depression, bradycardia, hypothermia, and alopecia. Thyroxine (T4) is used for the treatment of this disorder, and T4 is commonly administered with food. Thyroid hormones have a variety of physiological functions, and especially, circulating T4 levels have critical roles for the central nervous and the cardiovascular systems. Although T4 is commonly administered to the patient dogs with food, the influence of food intake on serum T4 levels remains to be elucidated. In the present study, we investigated the effects of food intake on the pharmacokinetics of orally administered T4 using 5 healthy beagle dogs. When T4 (10 μg/kg) was administered to the fasted dogs, serum T4 and free T4 (FT4) concentrations significantly increased, but triiodothyronine (T3) and thyroxine stimulating hormone (TSH) concentrations significantly decreased. However, when T44 was administered to the dogs with food, serum T4 and FT4 concentrations did not change statistically, and T3 and TSH concentrations significantly increased. We conclude that food intake with oral T4 administration maintained the serum T4 levels in the dogs as compared to oral T4 administration without food.
