The thyroid gland is located in the base of the neck on both sides of the lower part of the larynx (voice box) and upper part of the trachea (wind pipe). The gland produces thyroid hormone in response to stimulation by a hormone from the pituitary gland. Thyroid hormone acts throughout the body to regulate metabolism.

Thyroid diseases can be broadly divided into the following categories:

• Overproduction of thyroid hormone (hyperthyroidism)
• Underproduction of thyroid hormone (hypothyroidism)
• Benign (noncancerous) thyroid disease
• Thyroid cancer

For information about a specific type of thyroid disease see one of the following:

• Anaplastic carcinoma of the thyroid
• Chronic thyroiditis (Hashimoto's disease)
• Colloid nodular goiter
• Hyperthyroidism
• Hypopituitarism
• Hypothyroidism
• Hypothyroidism - primary
• Hypothyroidism - secondary
• Medullary thyroid carcinoma
• Painless (silent) thyroiditis
• Papillary carcinoma of the thyroid
• Subacute thyroiditis
• Thyroid cancer
• Congenital goiter