The thyroid is a small gland located in the front of the neck under the Adam's apple. It produces thyroid hormone, a chemical that regulates the body's metabolism. A swollen thyroid--which doctors call goiter--can be caused by a variety of conditions, reports the Mayo Clinic. Because some of these conditions, such as thyroid cancer, are serious, a physician should be consulted if the thyroid is enlarged.
Autoimmune Disorders
Autoimmune disorders--attacks of the thyroid gland by malfunctioning immune cells of a person's own body--cause the thyroid gland to swell. Hashimoto's disease--an autoimmune disorder in which the damaged thyroid is underactive--typically progresses slowly, with the thyroid swelling later in the course of the disease, reports the Mayo Clinic. In contrast, with Grave's disease, an autoimmune disorder that makes the eyes swell too, the thyroid produces too much thyroid hormone.
Nodules
The thyroid gland can be swollen if nodules are present, reports the Mayo Clinic. Multinodular goiter--several lumps on both sides of the thyroid--causes swelling in the entire thyroid. If there is a single nodule, called a solitary thryoid nodule, the swelling may appear on one side of the neck. Most nodules do not cause cancer.
Pregnancy
Certain hormones associated with pregnancy--including estrogen and human chorionic gonadotropin--weakly affect the thyroid, causing it to produce too little thyroid hormone, reports "Thyroid Disease and Pregnancy." This typically occurs in the first trimester and may cause a swollen thyroid, especially if the woman is not getting enough iodine. In up to 10 percent of women, the thyroid swells after pregnancy, which doctors believe is caused by a malfunctioning immune system similar to that of Hashimoto's syndrome, reports "Postpartum Thyroiditis."
Thyroid Cancer
Rarely, swelling may be caused by thyroid cancer, reports the Mayo Clinic. The swelling usually appears on one side of the thyroid.
Iodine Deficiency
A swollen thyroid is also caused by a lack of iodine in the diet, explains the Mayo Clinic. This usually occurs in regions of developing countries far from the sea, which contains iodine. A swollen thyroid from iodine deficiency is rare in the United States because iodine is routinely added to table salt.
References
- MayoClinic.com: Goiter
- Thyroid.org: Postpartum Thyroiditis
- Mayoclinic.com:Hashimoto's Disease
- American Thyroid Association: Hypothyroidism
- American Thyroid Association: Thyroid Disease and Pregnancy
