I. Where is the Thyroid Gland and What does it do?

The thyroid gland is  located in the neck. The gland has two lobes or parts that are located on either side of the trachea or windpipe usually just below the voice box. Cats can also have some thyroid gland tissue located in other parts of the neck and in the chest. One lobe or side of the normal thyroid gland in cats is about ¾ of an inch long by 1/8 of an inch wide and about 3/16 of an inch thick.

The thyroid gland is part of the endocrine system of the body. It produces a hormone called thyroxine. Thyroxine affects nearly every part of the body. It is important in regulating metabolism, energy level, heart rate and rhythm, and many other things.

II. What is Hyperthyroidism?

Hyperthyroidism in cats is caused 98-99% of the time by a thyroid adenoma. This is a benign growth of the thyroid gland that secretes thyroid hormone. Only about 1-2% of the time will hyperthyroidism in cats be caused by a malignant tumor of the thyroid gland.