The thyroid is a butterfly-shaped gland that is located in the lower neck and rests in front of the trachea (windpipe). One of the largest endocrine organs in the body, the thyroid produces hormones that help regulate growth and metabolism (how the body processes energy). Diseases of the thyroid gland typically include abnormalities in the production of thyroid hormone (either too much or too little hormone), or abnormalities in the anatomy or structure of the thyroid (such as a thyroid nodule).
Hypothyroid and Hyperthyroid
The most common functional abnormality of the thyroid gland is hypothyroidism. This occurs when the thyroid gland makes too little thyroid hormone. Common symptoms of hypothyroidism may include fatigue, unexplained weight gain, intolerance of cold, constipation, dry skin, brittle hair, joint and muscle pains, or difficulty with concentration.
A less common abnormality of the thyroid gland is hyperthyroidism. This occurs when the thyroid gland makes too much thyroid hormone. Common symptoms of hyperthyroidism may include racing heart, hand tremor, intolerance of heat, unexplained weight loss, anxiety, or insomnia. There are many different reasons why the thyroid gland might make too much or too little thyroid hormone.
Often, the thyroid gland functions normally, but there might be a structural or anatomical abnormality such as a thyroid nodule. These nodules are lumps that arise in an otherwise normal thyroid gland. Thyroid nodules are typically discovered by a physician during a routine office visit, or by imaging scans (ultrasound, CT scan, MRI) performed for other health reasons.
Thyroid nodules are very common, and are seen in up to 60 percent of women over the age of 50 years. The vast majority of thyroid nodules are noncancerous. In a small percentage of patients, the nodule may be cancerous. Thyroid cancer is uncommon and is typically a very treatable form of cancer, particularly when diagnosed early.
Some benign thyroid nodules make excessive amounts of thyroid hormone, and are referred to as “toxic nodules.” These nodules are almost never cancerous, but they can cause symptoms of hyperthyroidism and need to be treated.
An enlarged thyroid gland is called a goiter. Thyroid nodules are often present in enlarged thyroid glands, a condition referred to as a multinodular goiter. Goiters can sometimes cause pressure on other structures within the neck, including the esophagus and trachea. When severe, this can cause difficulty with swallowing and breathing. For some patients, the presence of a goiter can also be less desirable for cosmetic reasons. For all of the above reasons, surgery can be recommended.