Thyroiditis is the medical term for inflammation (swelling) of the thyroid gland, which can either cause abnormally low or high levels of thyroid hormones in the blood.

The thyroid gland is a butterfly-shaped gland found in the neck. It produces hormones that are released into the bloodstream to control the body’s growth and metabolism. They affect processes such as heart rate and body temperature, and help convert food into energy to keep the body going.

Symptoms vary depending on the type of thyroiditis. Common types are:

• Hashimoto’s thyroiditis (the most common)
• De Quervain’s or ‘subacute’ thyroiditis 
• Post-partum thyroiditis (triggered after giving birth)
• ‘Silent’ or painless thryoiditis 
• Drug-induced thyroiditis 
• Radiation-induced thyroiditis 
• Acute or infectious thyroiditis 

The symptoms and treatment of these conditions are briefly described below. 

Hashimoto’s thyroiditis 

In Hashimoto’s thyroiditis, your immune system mistakenly attacks your thyroid gland, causing it to gradually swell and become damaged.

The swollen thyroid gland may eventually cause a lump to form in your throat, known as a goitre.

As the thyroid gland is slowly destroyed over time, it is unable to produce sufficient amounts of thyroid hormone. The medical term for low levels of thyroid hormone in the blood is hypothyroidism.

This leads to symptoms of an underactive thyroid gland, which are very general and include:

• fatigue
• weight gain
• constipation
• dry skin
• depression

It may take months or even years for the condition to be detected, because the disease progresses very slowly.

The cause of Hashimoto’s thyroiditis is not understood, but in susceptible people it is thought to be triggered by smoking, infection, certain medications or possibly stress.

It may be associated with other conditions such as Addison’s disease, diabetes or hypoparathyroidism, runs in families, and is usually seen in females aged 30 to 50. 

Hashimoto’s thyroiditis cannot be cured as the low levels of thyroid hormone are usually permanent. However, symptoms are easily treated with thyroid hormone replacement, which is usually taken for life.

You may need surgery if your goitre is particularly large or there are suspicions of cancer.

Read about the treatment of an underactive thyroid and the treatment of goitre.

De Quervain’s thyroiditis 

De Quervain’s thyroiditis (sometimes called subacute thyroiditis) is a painful swelling of the thyroid gland that is thought to be triggered by a viral infection, such as mumps or the flu. 

It’s most commonly seen in females aged 20 to 50.

De Quervain’s thyroiditis usually causes a fever and pain in the neck, jaw or ear, and you may have any of the symptoms of an overactive thyroid gland, including:

• anxiety
• insomnia
• heart palpitations
• weight loss
• irritability

This is because it results in too much thyroid hormone in your blood, called thyrotoxicosis.

The palpitations and shakes associated with thyrotoxicosis can be treated with beta-blockers.

De Quervain’s thyroiditis settles down after a few days and is often followed by a spell of hypothyroidism (low levels of thyroid hormone) lasting a few weeks, before the thyroid gland recovers completely.

Post-partum thyroiditis 

Like Hashimoto’s thyroiditis, post-partum thyroiditis is caused by a problem with the immune system, but only happens in women who have recently given birth.

Up to four months after the birth, your immune system attacks your thyroid gland, causing the thyroid hormone inside to leak out into your blood. This causes a temporary rise in thyroid hormone levels (thyrotoxicosis), and symptoms similar to symptoms of an overactive thyroid gland, including:

• anxiety
• insomnia
• heart palpitations
• weight loss
• irritability

Then, after about four-to-eight months, your thyroid gland becomes depleted of thyroid hormone, leading to a fall in thyroid hormone levels (hypothyroidism). You may then get symptoms of an underactive thyroid gland, including:

• fatigue
• weight gain
• constipation
• dry skin
• depression

However, not every woman with post-partum thyroiditis will go through both these phases. 

If low thryoid hormone levels are causing severe symptoms, you may need to take thyroid hormone replacement until the condition gets better.

In most women with the condition, thyroid function returns to normal within 12 to 18 months after symptoms started.

Painless thyroiditis 

The symptoms of painless thyroiditis are similar to those of post-partum thyroiditis, but painless thyroiditis is not related to giving birth and can occur in both men and women. The cause is thought to be an immune system problem.

Like postpartum thyroiditis, there may be a phase of high thyroid hormone levels (thyrotoxicosis) followed by a phase of low thyroid hormone levels (hypothyroidism), before the symptoms eventually go away by about 12 to 18 months.

If low thyroid hormone levels are causing severe symptoms, you may need to take thyroid hormone replacement until the condition gets better.

Drug-induced thryoiditis 

Thyroiditis can also be triggered by the drugs interferon, amiodarone and a class of drugs to treat certain cancers (which include sunitinib), if these drugs damage the thyroid cells.

There may be symptoms of both high and low levels of thyroid hormone, but these are usually short-lived and get better after the drug treatment is stopped.

Radiation-induced thyroiditis 

Radioactive iodine treatment for an overactive thyroid gland or radiation therapy for certain cancers can also damage the thyroid gland, leading to symptoms of both high and low levels of thyroid hormone. 

The hypothyroidism (low levels of thyroid hormone) after radioactive iodine is usually permanent, causing symptoms of an underactive thyroid gland that will need to be managed with lifelong thyroid hormone replacement treatment. 

Acute or infectious thyroiditis 

Acute or infectious thyroiditis is usually triggered by a bacterial infection. Symptoms may include pain in the throat, feeling generally unwell, swelling of the thyroid gland and sometimes symptoms of a low or high level of thyroid hormones.

These symptoms will usually get better when the infection is treated with antibiotics. In the meantime, thyroid pain can be managed with non-steroidal anti-inflammatory painkillers such as ibuprofen.