The links on the page lead to definitions on the National Cancer Institute’s website.

The thyroid is a gland in the neck. It has two kinds of cells that make hormones. Follicular cells make thyroid hormone, which affects heart rate, body temperature, and energy level. C cells make calcitonin, a hormone that helps control the level of calcium in the blood.

The thyroid is shaped like a butterfly and lies at the front of the neck, beneath the voice box (larynx). It has two parts, or lobes. The two lobes are separated by a thin section called the isthmus.

A healthy thyroid is a little larger than a quarter. It usually cannot be felt through the skin. A swollen lobe might look or feel like a lump in the front of the neck. A swollen thyroid is called a goiter. Most goiters are caused by not enough iodine in the diet. Iodine is a substance found in shellfish and iodized salt.


The thyroid gland (a service of the National Cancer Institute)