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Human Anatomy

Picture of the Thyroid

The thyroid is a butterfly-shaped gland that sits low on the front of the neck. Your thyroid lies below your Adam’s apple, along the front of the windpipe. The thyroid has two side lobes, connected by a bridge (isthmus) in the middle. When the thyroid is its normal size, you can’t feel it.

Brownish-red in color, the thyroid is rich with blood vessels. Nerves important for voice quality also pass through the thyroid.

The thyroid secretes several hormones, collectively called thyroid hormones. The main hormone is thyroxine, also called T4. Thyroid hormones act throughout the body, influencing metabolism, growth and development, and body temperature. During infancy and childhood, adequate thyroid hormone is crucial for brain development.

Thyroid Conditions

Goiter: A general term for thyroid swelling. Goiters can be harmless, or can represent iodine deficiency or a condition associated with thyroid inflammation called Hashimoto’s thyroiditis.
Thyroiditis: Inflammation of the thyroid, usually from a viral infection or autoimmune condition. Thyroiditis can be painful, or have no symptoms at all.
Hyperthyroidism: Excessive thyroid hormone production. Hyperthyroidism is most often caused by Graves disease or an overactive thyroid nodule.
Hypothyroidism: Low production of thyroid hormone. Thyroid damage caused by autoimmune disease is the most common cause of hypothyroidism .
Graves disease: An autoimmune condition in which the thyroid is overstimulated, causing hyperthyroidism.
Thyroid cancer: An uncommon form of cancer, thyroid cancer is usually curable. Surgery, radiation, and hormone treatments may be used to treat thyroid cancer.
Thyroid nodule: A small abnormal mass or lump in the thyroid gland. Thyroid nodules are extremely common. Few are cancerous. They may secrete excess hormones, causing hyperthyroidism, or cause no problems.
Thyroid storm: A rare form of hyperthyroidism in which extremely high thyroid hormone levels cause severe illness.

Thyroid Tests

Anti-TPO antibodies: In autoimmune thyroid disease, proteins mistakenly attack the thyroid peroxidase enzyme, which is used by the thyroid to make thyroid hormones.
Thyroid ultrasound: A probe is placed on the skin of the neck, and reflected sound waves can detect abnormal areas of thyroid tissue.
Thyroid scan: A small amount of radioactive iodine is given by mouth to get images of the thyroid gland. Radioactive iodine is concentrated within the thyroid gland.
Thyroid biopsy: A small amount of thyroid tissue is removed, usually to look for thyroid cancer. Thyroid biopsy is typically done with a needle.
Thyroid stimulating hormone (TSH): Secreted by the brain, TSH regulates thyroid hormone release. A blood test with high TSH indicates low levels of thyroid hormone (hypothyroidism), and low TSH suggests hyperthyroidism.
T3 and T4 (thyroxine): The primary forms of thyroid hormone, checked with a blood test.
Thyroglobulins: A substance secreted by the thyroid that can be used as a marker of thyroid cancer. It is often measured during follow-up in patients with thyroid cancer. High levels indicate recurrence of the cancer.
Other imaging tests: If thyroid cancer has spread (metastasized), tests such as CT scans, MRI scans, or PET scans can help identify the extent of spread.