In some cases, no definite cause for goitres can be identified. However, there are a number of different possible causes that are outlined below.
Iodine deficiency
Iodine deficiency used to be the major cause of goitres, and it still remains a significant problem in parts of the developing world.
Iodine is a trace element that is found in seawater and soil. It enters the food chain through plants that grow in iodine-rich soil, or through fish or plants from the sea. Iodine is found in:
- seafood, such as fish, shellfish or seaweed
- plant foods, such as cereals or grains
- cow’s milk
The thyroid gland (a gland in the neck that produces hormones) needs iodine to help manufacture thyroid hormones (chemicals released into the bloodstream that control the body's growth and metabolism). If your body does not receive enough iodine, your thyroid gland will expand in order to produce more thyroid hormones.
In the UK, iodine deficiency used to be a common problem until, in the early 1900s, salt manufactures started to add small amounts of iodine to salt, which reduced the number of cases.
However, in recent years, the number of people experiencing iodine deficiency in the UK has started to rise. This could be due to an increased number of people preferring a low-salt, non-dairy diet. Iodine deficiency can be a problem for people who are following a strict vegan diet.
Over-active thyroid gland
A goitre can develop if the thyroid gland becomes over-active (hyperthyroidism), leading to an excessive amount of thyroid hormones being produced. Increased hormone production over-stimulates the thyroid gland and causes it to swell.
The leading cause of hyperthyroidism is a condition called Graves' disease. Graves' disease causes your immune system (the body’s natural defence system) to send antibodies (proteins that fight infections) to your thyroid gland. The antibodies attack the thyroid gland, causing an increased amount of thyroid hormones to be released.
See the Heath A-Z topic about Hyperthyroidism for more information about this condition.
Under-active thyroid gland
A goitre can also develop if the thyroid gland becomes under-active (hypothyroidism). If the thyroid gland does not produce enough thyroid hormones, the body will stimulate the gland to produce more. This can cause the thyroid gland to swell.
As well as iodine deficiency, one of the leading causes of hypothyroidism is a condition called Hashimoto's thyroiditis, which is sometimes also known as Hasimoto's disease.
As with Graves' Disease, Hashimoto's thyroiditis causes the immune system to attack the thyroid gland. Rather than over-stimulating the gland, Hashimoto's thyroiditis interferes with the gland's ability to produce hormones. In order to compensate for this, the body causes the gland to swell, resulting in a goitre.
See the Health A-Z topic about Hypothyroidism for more information about this condition.
Smoking
There may also be a link between smoking and an increased risk of developing a goitre. This may be because tobacco smoke contains a chemical called thiocyanate, which can interfere with the body's ability to make use of iodine.
Smokers who have a low-iodine diet are particularly at risk. See the Health A-Z topic about Quitting smoking for information and advice about how to stop smoking.
Other causes
A number of other causes have been linked to goitres. These are outlined below.
Pregnancy and puberty
The changes in hormone levels that occur during pregnancy and puberty (when a child gradually progresses to a sexually developed adult) can affect the thyroid gland.
Lithium
Lithium is a medicine that is often used to treat a number of mental health conditions, such as depression and bipolar disorder (a condition that affects your moods, which can swing from one extreme to another). Lithium can interfere with how your thyroid gland functions.
Infection
A number of bacteria, parasites, and fungi that cause infections are also known to cause goitres.
Goitrogenic foods
Goitrogenic foods are foods that if eaten in excess are known to suppress the function of the thyroid gland. They include:
- spinach
- peanuts
- soybeans
- tofu
Excessive iodine
An excessive amount of iodine can build up in the body as a result of eating an excessive amount of iodine-rich food. For example seaweed, particularly kelp (a type of brown seaweed that contains many different minerals), is a rich source of iodine. An excess amount of iodine can affect the thyroid gland.
Exposure to radiation
Exposure to radiation (energy waves that travel through the air) can sometimes cause goitres. Radiation is used to treat some health conditions (radiotherapy), such as cancer. Receiving radiotherapy to the neck can sometimes cause goitres.
Non-cancerous growths
Non-cancerous growths can also sometimes cause goitres.
Thyroid cancer
Thyroid cancer is another possible cause of goitres, although it is rare in the UK. Cancer research UK estimate that six out of every 1,000 cancers diagnosed in the UK are thyroid cancer.
See the Health A-Z topic about Thyroid cancer for more information about this condition.
