Thyromegaly is a disorder in which the thyroid gland — the butterfly-shaped gland in the neck — becomes abnormally enlarged. Thyromegaly is more commonly known as a goiter. It’s most often caused by insufficient iodine in the diet, but it can also result from other conditions.
The swollen thyroid gland is often visible on the outside of the neck and can cause difficulty with breathing and swallowing. If not treated, thyromegaly can cause the thyroid gland to stop making enough thyroid hormone (hypothyroidism) or to produce too much thyroid hormone (hyperthyroidism).
The thyroid gland secretes two important hormones — thyroxine (T4) and triiodothyronine (T3). These hormones are involved in the regulation of your body’s metabolism, heart rate, respiration, digestion, and mood.
The production and release of these hormones is regulated by the pituitary gland. The pituitary gland makes a hormone called thyroid-stimulating hormone (TSH). TSH is responsible for telling the thyroid if it needs to release more T4 and T3.
Thyromegaly may occur when your thyroid is producing either too much or too little thyroid hormone. In other cases, hormone production is normal, but lumps (nodules) on the thyroid cause it to enlarge.
Causes of thyromegaly include:
The most common cause of thyromegaly in developing countries is a deficiency of iodine. Iodine is essential for T4 and T3 hormone production. Iodine is mostly found in seawater and in soil near the coast.
In developed countries, iodine is added to table salt and other foods so iodine deficiencies aren’t common. It’s still helpful to be familiar with the symptoms of an iodine deficiency.
In the developing world, however, many people who live far from the ocean or at higher elevations don’t get enough iodine in their diets. It’s estimated that roughly one-third of the global population has a low iodine intake.
Since the thyroid can’t make enough hormone, it enlarges to compensate.
Graves’ disease is an autoimmune disease. It occurs when the immune system mistakenly attacks the thyroid gland. In response, the thyroid becomes overstimulated and begins to release excess hormones, which causes hyperthyroidism. The thyroid then swells.
Hashimoto’s thyroiditis is also an autoimmune disorder. In Hashimoto’s, the thyroid gland is damaged and can’t produce enough hormone (hypothyroidism). In response, the pituitary gland makes more TSH in an effort to stimulate the thyroid. This causes the thyroid to swell.
The thyroid gland can also enlarge when solid or fluid-filled nodules grow on the gland.
When there’s more than one nodule on the thyroid, it’s called multinodular goiter. When there’s only one nodule, it’s referred to as a solitary thyroid nodule.
These nodules are usually noncancerous (benign), but they may produce their own thyroid hormone and cause hyperthyroidism.
During pregnancy, the body produces extra hormones. One such hormone, known as human chorionic gonadotropin (hCG), can cause the thyroid gland to enlarge.
Inflammation of the thyroid is called thyroiditis. Thyroiditis can be caused by:
- an infection
- an autoimmune disease, such as Hashimoto’s or Graves’ disease
- medications, such as interferon and amiodarone
- radiation therapy
Inflammation can make the thyroid hormone leak out into the bloodstream and the thyroid gland to swell.
Some medications, such as lithium, can cause thyromegaly, though the exact reason why is unknown. This type of thyromegaly doesn’t affect the production of thyroid hormone. Though the thyroid is enlarged, its function is healthy.
The main symptom of thyromegaly is an enlarged thyroid gland, sometimes so large that it’s noticeably visible at the front of the neck.
The enlarged area can put pressure on your throat, which can cause the following symptoms:
- difficulty swallowing or breathing
- tightness in the neck
Thyromegaly that occurs as a result of hypothyroidism or hyperthyroidism is associated with a number of symptoms.
Symptoms associated with hypothyroidism include:
- always feeling cold
- dry skin and hair
- weight gain
- stiff joints
Symptoms associated with hyperthyroidism include:
- increased appetite
- trouble concentrating
- difficulty sleeping
- brittle hair
- irregular heartbeat
A doctor can diagnose thyromegaly during a physical examination of the neck.
During a routine examination, a doctor feels around the neck and asks you to swallow. If your thyroid is found to be enlarged, your doctor will want to determine the underlying cause.
Diagnosing the underlying cause of thyromegaly may involve:
- thyroid hormone tests to measure the amount of T4 and TSH in the blood
- ultrasound to create an image of the thyroid gland
- thyroid scan to produce an image of your thyroid on a computer screen using a radioactive isotope injected into the vein on the inside of your elbow
- biopsy to take a sample of tissue from the thyroid using a fine needle; the sample is sent to a laboratory for testing
- antibody tests
Thyromegaly is usually treated only when it causes symptoms. Treatment depends on the underlying cause.
Thyromegaly caused iodine deficiency
Small doses of iodine may help shrink the thyroid gland and reduce symptoms. If the gland doesn’t shrink, you may need surgery to remove all or part of the gland.
Hashimoto’s thyroiditis is usually treated with synthetic thyroid hormone replacement such as levothyroxine (Levothroid, Synthroid).
Treatment may include medications to lower the production of thyroid hormones, such as methimazole (Tapazole) and propylthiouracil.
If these medications fail to keep your thyroid hormones in check, a doctor may use either radioactive iodine therapy or surgery (thyroidectomy) to destroy the thyroid gland. You will need to take synthetic thyroid hormones on an ongoing basis following surgery.
Thyromegaly during pregnancy
Thyromegaly during pregnancy can lead to complications, such as premature birth and low birth weight. If a pregnant women with thyromegaly has an overactive thyroid, she’ll likely be treated with medications like propylthiouracil or methimazole. Surgery and radioiodine therapy aren’t recommended during pregnancy.
If a pregnant woman with thyromegaly has an underactive thyroid, synthetic thyroid hormones are recommended.
Thyromegaly caused by nodules
Whether or not any treatment is given for thyromegaly caused by nodules depends on these factors:
- if the nodules cause hyperthyroidism
- if the nodules are cancerous
- if the goiter is large enough to cause other symptoms
Your doctor might not treat nodules that aren’t cancerous and aren’t causing symptoms. Instead, they’ll closely monitor the nodules over time.
If the nodule is overproducing thyroid hormones and causing hyperthyroidism, one option is to take synthetic thyroid hormones. The pituitary gland should detect the extra thyroid hormone and send a signal to the thyroid to lower its production.
A doctor may also choose to destroy the thyroid gland using radioactive iodine or surgery.
Thyromegaly caused by inflammation
Pain can be managed with mild anti-inflammatory medications like aspirin or ibuprofen. If the swelling is severe, a doctor might prescribe an oral steroid like prednisone.
It’s not quite understood why nodules increase the risk for cancer. Doctors recommend that anyone with thyromegaly caused by nodules on their thyroid gland be screened for cancer. A biopsy of a thyroid nodule can determine if a nodule is cancerous.
The outlook for thyromegaly depends on the underlying cause and the size of the goiter. It’s possible to have thyromegaly and not even know it. Small goiters that don’t cause problems aren’t a concern at first, but the goiter could grow larger in the future, or start producing too much or too little thyroid hormone.
Most causes of thyromegaly are treatable. Surgery may be required if swollen thyroid causes problems with breathing and swallowing or it’s producing excess hormone.
In rare cases, thyromegaly that results from nodules on the thyroid can lead to thyroid cancer. Surgery must be done if cancer is present. When diagnosed in its early stages, most people with thyroid cancer respond well to treatment. The 5-year survival rate for people diagnosed with thyroid cancer is 98.1 percent.
Visit your doctor if you notice any swelling in the front of your neck or any other symptoms of thyromegaly.