It is one of the most common thyroid disorders.
Goiters are often harmless but symptoms can occur, and treatment may be required depending on the size and type of goiter.
Here are some key points about goiter. More detail and supporting information is in the body of this article.
- Goiter describes a condition where the thyroid gland, located in the neck, becomes enlarged.
- In developed countries, goiter is usually caused by an autoimmune disease.
- Goiter is usually diagnosed by physical examination, but thyroid function blood tests and scans may be used.
- Treatment is not necessary unless the goiter is large and causes symptoms.
What is goiter?
The thyroid gland. An underactive gland can cause weight gain.
A goiter is an enlarged thyroid gland.
The thyroid gland is situated in front of the windpipe and is responsible for producing and secreting hormones that regulate growth and metabolism.
Most cases are categorized as 'simple' goiters that do not involve inflammation or any detriment to thyroid function, produce no symptoms, and often have no obvious cause.
Some people experience a small amount of swelling. Others can have considerable swelling that constricts the trachea and causes breathing problems.
The degree of swelling and the severity of symptoms produced by the goiter depends on the individual.
Most goiters produce no symptoms. When symptoms do occur, the following are most common:
- throat symptoms of tightness, cough, and hoarseness
- trouble swallowing
- in severe cases, difficulty breathing, possibly with a high-pitch sound
Other symptoms may be present because of the underlying cause of the goiter, but they are not because of the goiter itself. For example, an overactive thyroid can cause symptoms such as:
- increased sweating
- heat hypersensitivity
- increased appetite
- hair loss
- weight loss
In cases where goiter is a result of hypothyroidism, the underactive thyroid can cause symptoms such as:
- cold intolerance
- personality changes
- hair loss
- weight gain
Aside from the swelling itself, many people with goiter present no symptoms or signs at all.
Goiter can be caused by a number of different conditions:
Deficiency of iodine - found in seafood - is a major cause of goiter.
Iodine deficiency is the major cause of goiter worldwide, but this is rarely a cause in more economically developed countries where iodine is routinely added to salt.
As iodine is less commonly found in plants, vegan diets may lack sufficient iodine. This is less of a problem for vegans who live in countries such as the United States that add iodine to salt.
Dietary iodine is found in:
- plant food grown in iodine-rich soil
- cow's milk
In some parts of the world, the prevalence of goiters can be as high as 80 percent, such as in the remote mountainous regions of southeast Asia, Latin America, and central Africa. In these places, daily intake of iodine can fall below 25 micrograms (mcg) per day, and children are often born with hypothyroidism.
The thyroid gland needs iodine to manufacture thyroid hormones, which regulate the metabolism.
The main cause of goiter in developed countries is autoimmune disease. Women over the age of 40 are at greater risk of goiter, as are people with a family history of the condition.
Hypothyroidism is the result of an underactive thyroid gland, and this causes goiter. Because the gland produces too little thyroid hormone, it is stimulated to produce more, leading to the swelling.
This usually results from Hashimoto's thyroiditis, a condition in which the body's immune system attacks its own tissue and causes inflammation of the thyroid gland.
Hyperthyroidism, or an overactive thyroid gland, is another cause of goiter. Too much thyroid hormone is produced. This usually happens as a result of Graves' disease, an autoimmune disorder where the body's immunity turns on itself and attacks the thyroid gland, causing it to swell.
Less common causes of goiter include the following:
- Smoking: Thiocyanate in tobacco smoke interferes with iodine absorption.
- Hormonal changes: Pregnancy, puberty, and menopause can affect thyroid function.
- Thyroiditis: Inflammation caused by infection, for example, can lead to goiter.
- Lithium: This psychiatric drug can interfere with thyroid function.
- Overconsumption of iodine: Too much iodine can cause a goiter.
- Radiation therapy: This can trigger a swollen thyroid, particularly when administered to the neck.
Most simple goiters are preventable through adequate intake of iodine, which is added to table salt in many countries.
Active treatment of goiter is reserved for cases that cause symptoms. If the goiter is small and thyroid function is normal, treatment is not usually offered.
The diagnosis of a goiter is possible with physical examination of the neck, palpating for the swelling. The doctor may ask the patient to swallow while feeling for the goiter.
Ultrasound scans may be used to visualize the thyroid gland.
Once a goiter is diagnosed, the doctor may wish to uncover any underlying problems with thyroid function, for example, because of hyper- or hypothyroidism.
Thyroid function tests are blood tests that measure levels of TSH and T4. A carefully controlled feedback mechanism means that TSH stimulates the thyroid to produce more thyroxine, while T4 tells the thyroid to stop producing as much thyroxine.
With an overactive thyroid, TSH levels are low or non-existent, and T4 levels are high. In people with underactive thyroid, the reverse is true. TSH levels are high and T4 levels are low.
Another hormone, triiodothyronine, is measured in some cases of an overactive gland, such as suspected Graves' disease.
In some cases of goiter, specialist tests may be arranged, such as:
- Radioactive iodine scan: This provides a detailed picture of the gland following an injection of radioactive iodine.
- Ultrasound scan: This assesses the gland and the size of the goiter.
- Fine-needle aspiration: A biopsy to remove a sample of cells from within the gland may be performed if, for example, cancer is suspected.
In cases caused by underactive thyroid or hypothyroidism, treatment is a synthetic replacement of thyroid hormone.
The dosage of synthetic thyroxine (T4) is gradually increased until measurements indicate normal thyroid function has been restored.
Synthetic preparations of T4 are preferred, but preparations of thyroid-stimulating hormone (TSH) and combinations of both may be tried, as may desiccated animal thyroid extract.
In goiters caused by overactive thyroid or hyperthyroidism, treatment aims to counter the excess hormone production. For instance, anti-thyroid drugs, such as thionamide drugs, gradually reduce excessive hormone levels.
Radioactive iodine to decrease thyroid function and stop hormone production is also a treatment option for hyperthyroidism.
Surgery to reduce the size of swelling is reserved for cases where the goiter is causing troublesome symptoms, such as difficulty breathing or swallowing.
Thyroidectomies are performed under general anesthetic to remove part of the thyroid gland.
There are several main types of goiter:
- Diffuse smooth goiter: This occurs when the entire thyroid swells.
- Nodular goiter: A lump develops on the thyroid. These are extremely common. If many lumps develop, this is known as multinodular goiter.
- Retrosternal goiter: This type of goiter can grow behind the breastbone. This can constrict the windpipe, neck veins, or esophagus, and sometimes requires surgery.
The type of goiter will dictate how it is treated and the symptoms that may show.