Goitre - Causes of goitre

Goitres can have many possible causes. Sometimes, a cause can't be identified.

Iodine deficiency

Iodine deficiency used to be the primary cause of goitre, but dietary changes mean it's now rare in the UK. However, it remains a significant problem in parts of the developing world.

Iodine is a trace element 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 doesn't receive enough iodine, your thyroid gland becomes underactive and increases in size, in order to produce more thyroid hormones.

Until the early 1900s, iodine deficiency used to be a common problem in the UK. Around this time, salt manufacturers started adding 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 preference for a low-salt, non-dairy diet. Iodine deficiency can be a problem for people who follow a strict vegan diet (where meat, eggs, dairy foods and all other animal-derived products are excluded).

Overactive thyroid gland

A goitre can develop if the thyroid gland becomes overactive (hyperthyroidism), resulting in too much thyroid hormone 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. This causes your immune system (the body’s natural defence system) to send antibodies (proteins that fight infections) to your thyroid gland. The antibodies stimulate the thyroid gland, causing an increased amount of thyroid hormones to be released.

Underactive thyroid gland

A goitre can also develop if the thyroid gland becomes underactive (hypothyroidism). If the thyroid gland doesn't produce enough thyroid hormones, your body will stimulate it 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 known as Hashimoto's disease.

As with Graves' disease, Hashimoto's thyroiditis is an autoimmune condition. However, rather than over-stimulating the gland, it causes inflammation within the thyroid gland and interferes with its ability to produce hormones. To compensate for this, the body causes the gland to swell, resulting in a goitre.

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 utilise iodine.

People who smoke and have a low-iodine diet are particularly at risk. Read more about how to stop smoking.

Other causes

Many other causes have been linked to goitres, which are outlined below.

Pregnancy, the menopause and puberty

The changes in hormone levels that occur during pregnancy, the menopause and puberty (sexual maturation) can affect the thyroid gland.

Lithium

Lithium is a medicine that's 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.

Inflammation

The thyroid gland can become inflamed. This condition is known as thyroiditis, and it can sometimes occur after pregnancy, as a result of certain viral and bacterial infections, or after taking certain medications. Thyroiditis can cause a painful goitre to develop.

Excessive iodine

Too much iodine can build up in the body as a result of eating too much iodine-rich food. Seaweed, for example, particularly kelp, is a rich source of iodine. Having too much in the body can affect the thyroid gland.

Radiation exposure

Radiation exposure can sometimes cause goitres. Radiation, in the form of radiotherapy, is often used to treat certain health conditions, such as cancer. Having radiotherapy to the neck can sometimes cause goitres.

Nodules within the thyroid

Single or multiple nodules within the thyroid gland can cause goitres. Most thyroid nodules are benign (non-cancerous), but all nodules need to be assessed thoroughly to exclude thyroid cancer (see below).

Thyroid cancer

Thyroid cancer is another possible cause of goitres, although it's rare in the UK. Cancer Research UK estimates that less than 1 in every 100 cancers diagnosed in the UK is thyroid cancer.