• Medium to large dogs, such as golden retrievers, are more susceptible to thyroid cancer.golden retriever image by totti from Fotolia.com
  
  Thyroid glands are located in the neck and produce hormones that effect body function and growth through the entire dog, according to Washington State Universities College of Veterinary Medicine. Though rare, tumors sometimes arise from the thyroid gland. Fetchdog.com defines benign, nonspreading cancers as adenomas, and malignant, spreading cancers are called carcinomas. Carcinomas are unfortunately more rare in dogs than adenomas and are usually discovered after noticing a swelling in the dog's neck.
  
  

Hyperthyroidism

• Overactive thyroid glands, or hyperthyroidism, is usually the result of benign tumors. Hyperthyroidism usually presents itself with restless behavior, drinking and urinating more than usual or hair coat abnormalities. These symptoms are not generally associated with malignant tumors and are rare.
  
  

Difficulty Breathing

• Coughing and difficulty in breathing are common signs of a tumor that compresses the dog's windpipe. At this stage it is difficult to tell whether the difficulty in breathing is due to a thyroid tumor or some other complication. Consult a veterinarian to diagnose the problem.
  
  

Difficulty Swallowing

• Esophagus compression is the result of tumor growth in the thyroid. In this case the dog may experience difficulty swallowing. Your dog may eat slowly, showing reduced enthusiasm at feeding times.
  
  

Bark Pitch

• Voice box nerves are sometimes affected by the presence of a thyroid tumor, resulting in a change in the tone of the dog's bark. If you notice a change over time of your dog's bark pitch, whether slowly or suddenly, consult a veterinarian.