A simple, reliable method for producing hypothyroidism in the dog and thyroid function tests in normal and hypothyroid dog

Hypothyroidism is a common and generalized disorder which is seen in both animals and man. Although it can be easily produced experimentally in the rat, it is difficult to produce in the dog. We have evaluated various techniques used to induce this disorder in the dog, and present a new reliable method which is a modification of the use of ¹³¹I. Surgical thyroidectomy was unsuccessful and small doses of ¹³¹I with prior TSH stimulation with and without previous surgical thyroidectomy were unreliable. The administration of large doses of ¹³¹I (2 mCi/ kg) following TSH stimulation produced hypothyroidism in all attempts. The radioactive iodine uptake of the thyroid gland, triiodothyronine resin uptake and serum cholesterol were reliable determinants of thyroid function and were significantly different in the normal and hypothyroid dogs. In addition, the serum cholesterol was found to be useful in following the dog's thyroid state during therapy.