The degree of swelling and the severity of symptoms produced by the goiter depends on the individual.
Some cases involve a small amount of swelling, whereas others can involve considerable swelling that actually constricts the trachea and causes breathing problems.
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.
Fast facts on 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.
- Iodine deficiency is the world's leading cause of goiter - but this is rare in North America.
- 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 (there are often no symptoms).
What causes goiter?
Goiter can be caused by a number of different conditons:
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 populations in the remote mountainous regions of southeast Asia, Latin America, and central Africa, where daily intake of iodine can fall below 25 micrograms a day and children are often born with hypothyroidism.
The thyroid gland needs iodine to manufacture thyroid hormones, which regulate the body's rate of 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 within the thyroid gland.
Hyperthyroidism - 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.
Other causes of goiter
Less common causes of goiter include the following:
- nodules - benign lumps
- 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
- lithium - a psychiatric drug that can interfere with thyroid function
- overconsumption of iodine - too much iodine can cause a goiter
- radiation therapy - particularly to the neck
Treatments for goiter
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 - otherwise, no action is taken, and some simple goiters resolve on their own. If the goiter is small and thyroid function is normal, treatment is not usually offered.
The thyroid gland. An underactive gland can cause weight gain.
In cases caused by underactive thyroid or hypothyroidism, treatment is with a synthetic replacement of thyroid hormone.
The dosage of synthetic thyroxine is gradually increased until measurements indicate normal thyroid function has been restored.
Synthetic preparations of T4 (l-thyroxine) are preferred, but preparations of T3 (liothyronine) 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 excess 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 the 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.
Diagnosis of goiter
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.
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 thyroid-stimulating hormone (TSH), and thyroxine (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.
In overactive thyroid, TSH levels are low or non-existent, and T4 levels are high. In underactive thyroid, the reverse is true; TSH levels are high, and T4 low.
Another hormone - triiodothyronine - is measured in some cases of an overactive gland, such as suspected Graves' disease.
Ultrasound scans may be used to visualize the thyroid gland.
In some cases of goiter, specialist tests may be arranged, such as:
- Radioactive iodine scan - to provide a detailed picture of the gland following an injection of radioactive iodine.
- Ultrasound scan - to assess the gland and the size of the goiter.
- Fine-needle aspiration - a biopsy to remove a sample of cells from within the gland (this may be performed if, for example, cancer is suspected).
Signs and symptoms of goiter
Most goiters are asymptomatic (produce no symptoms). The following are the most common symptoms that are seen with goiter:
- throat symptoms of tightness, cough, and hoarseness
- trouble swallowing (dysphagia)
- 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, if the cause is hyperthyroidism, the 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 cases of goiter present no symptoms or signs at all.