Usually when you have an infection of the upper respiratory tract you soon recover. However, in rare instances, the upper respiratory tract infection can cause an unexpected immune response in the thyroid gland (which sits at the front of the neck) called subacute thyroiditis. It causes a painful swelling of the thyroid caused by the inflammatory response. Subacute thyroiditis is also known as De Quervain’s thyroiditis, subacute non-suppurative thyroiditis, giant cell thyroiditis and subacute granulomatous. It can be a cause of hypothyroidism in the short and long-term and hyperthyroidism in the short term.

Subacute thyroiditis is very rare with just 4.9 cases per 100,000 people per year. However, there is emerging evidence that in some patients with Covid, there is the development of subacute thyroiditis and this may change the prevalence data in due course.

What are the symptoms of subacute thyroiditis?

Subacute thyroiditis is typically painful in the neck and throat area (although silent, or painless, subacute thyroiditis is possible). There will be a notable swelling in the thyroid area, at the front of the neck. There may be occasional and temporary weakness or paralysis of the vocal chords, affecting the sufferer’s voice.

The thyroid gland looks like a butterfly, with two lobes. It’s not unusual for the pain to present only in one lobe in the early stages, but it quickly affects the whole thyroid. Due to the location, those with subacute thyroiditis often experience pain radiating through the jaw and up towards their ears. In the early stages, a fever is common. Acute symptoms typically last a few weeks and then fluctuate until the condition subsides.

During subacute thyroiditis, the pain is likely to be worse when applying pressure to the thyroid gland, including when swallowing, making eating and drinking sometimes difficult. Alongside this, it is common to experience fatigue and lethargy.

As well as this, there are likely to be signs of hyperthyroidism, occurring because the inflammation is causing the thyroid gland to release too much thyroid hormone. These symptoms include:

• Increased frequency of bowel movements, including loose stools and diarrhea.
• Hair falling out and thinning.
• Intolerance to heat and feeling overly warm.
• Irregular menstrual cycles in women.
• Irritability and mood change.
• Anxiety and heightened nervousness.
• Tremors.
• Fast heart rate (palpitations or tachycardia).
• Increased sweating.
• Notable weight loss.
• Increased appetite.

Your thyroid gland is very finely tuned and balanced. As such, as you heal, things may swing the other way and it in turn releases too little thyroid hormone and can give you the symptoms of hypothyroidism. In this case, you may experience the mirror image of some of the above symptoms, as well as other symptoms:

• Decreased frequency of bowel movements, including constipation.
• Intolerance to cold and struggling to get warm.
• Irregular menstrual cycles in women.
• Fatigue and lethargy.
• Notable weight gain.
• Reduced appetite.
• Dry skin.
• Mood changes.

These diverse symptoms often settle back to normal over the course of the condition, but you may need treatment, especially for an underactive thyroid, during this time. In some very rare cares, the hypothyroidism triggered by subacute thyroiditis can become permanent.

What causes subacute thyroiditis?

It’s believed that subacute thyroiditis is caused by a viral condition and this fits with most patients’ history immediately prior to becoming unwell with thyroid symptoms. Commonly patients may have had mumps, influenza, or an ear, sinus or throat infection a few weeks beforehand. It is more common in women, especially those aged 45+.

How is subacute thyroiditis diagnosed?

Subacute thyroiditis is rare. It is diagnosed through patient history and laboratory tests including looking at:

• TSH (thyroid stimulating hormone) levels
• T4 (thyroxine) and T3 levels
• Radioactive iodine uptake
• CRP (c-reactive protein)
• ESR (erythrocyte sedimentation rate)
• Thyroglobulin level

You may also have an ultrasound done of your thyroid gland, or very occasionally, a biopsy.

How is subacute thyroiditis treated?

Predominantly, the goal of treatment is to manage and reduce the pain caused by the swelling of the thyroid gland. Commonly used medications for this include ibuprofen (such as Advil) and aspirin. Where swelling is really severe, other drugs to reduce inflammation may be needed, such as the steroid prednisone.

If you are experiencing hyperthyroidism symptoms then these may be managed with beta blockers. Alternatively, if you are experiencing hypothyroidism symptoms then you may need replacement thyroid hormone, by taking levothyroxine.

Beyond managing symptoms, typically subacute thyroiditis improves on its own.

How long does subacute thyroiditis last?

After an acute beginning, it’s not unusual for it to take some time to fully recover from subacute thyroiditis. Initial symptoms may last for between 1-3 months, with full recovery sometimes taking up to 18 months. In 5% of sufferers, permanent hypothyroidism remains. Apart from this, other complications don’t usually occur.

Whilst the initial triggering viral illness may have been infectious, subacute thyroiditis itself is not infectious.

You will want to manage your subacute thyroiditis with the support of a doctor.

Can you prevent against subacute thyroiditis?

Unfortunately, there’s not much you can do to prevent getting subacute thyroiditis. However, vaccines that reduce your likelihood of getting viral infections, such as flu and MMR are likely to prevent it.

Is Covid causing subacute thyroiditis?

There have been various reports of Covid triggering subacute thyroiditis and some research has begun into this, especially in Milan. It does appear that subacute thyroiditis is more frequent in patients with severe Covid. The Milan study showed 15% of High Dependency Unit patients had thyrotoxicosis caused by subacute thyroiditis. Interestingly, the majority were men, which is not the case typically.

Studies and research is ongoing to look more into Covid and subacute thyroiditis and thyroid abnormalities in Long Covid patients. It may be that some of the research in this regard will ultimately lead to prevention and treatment changes for those suffering from subacute thyroiditis triggered by other viruses.

Get the right care

If you believe that you may have subacute thyroiditis or another thyroid condition, or have any concerns for your health following a viral infection, you should contact your GP in the first instance. The information given here is for guidance only and doesn’t substitute professional medical advice.