Introduction to Thyroid Cancer

The Thyroid Gland

The thyroid gland is located in the front part of the neck below the larynx (voice box) and just above the clavicle (collarbone). Its shape resembles that of a "bow tie" consisting of two lobes (right and left) that are joined together in the middle by the isthmus. The thyroid is one of the most important endocrine glands because it regulates the body's metabolism, growth, and development. The thyroid gland is composed of two types of cells:

• Follicular cells - Most of the thyroid consists of thyroid follicle cells that produce and store thyroid hormones called thyroxine (T4) and triiodothyronine (T3). The follicular cells also produce a protein called thyroglobulin.

• Parafollicular cells - Also known as "C cells", the parafollicular cells produce and secrete a hormone called calcitonin that helps to regulate the levels of calcium in the body.

Disorders of the thyroid gland are relatively common and affect millions of people worldwide. In most cases, patients present to a doctor's office with classic symptoms suggestive of a thyroid disorder while in others a routine physical examination or a blood test will uncover a disorder of the thyroid gland. In general, disorders of the thyroid gland include:

• Hyperthyroidism
• Hypothyroidism
• Benign thyroid nodules
• Malignant thyroid tumors