Subacute Thyroiditis (De Quervain's Thyroiditis)

How subacute thyroiditis happens

The thyroid stores a large supply of thyroid hormone in tiny follicles. In subacute thyroiditis, inflammation damages these follicles, often 2 to 8 weeks after a viral illness such as a cold, flu, mumps or COVID-19. The stored hormone spills into the blood, causing temporary hyperthyroidism. Because the damaged gland cannot make new hormone, levels then fall. When the gland heals, production returns.

Under the microscope the thyroid shows clusters of large "giant cells" and granulomas, which is why it is also called granulomatous or giant cell thyroiditis. It is not an autoimmune disease like Hashimoto's, and it rarely comes back.

Phases of subacute thyroiditis

Not everyone goes through every phase. Some people have only the painful thyrotoxic phase and recover directly. About 5 to 15% are left with permanent hypothyroidism.

Symptoms

• Pain at the front of the neck, often starting on one side and moving to the other ("creeping thyroiditis"). It can spread to the jaw, ear or throat and is worse on swallowing or turning the head. People sometimes mistake it for a sore throat, toothache or ear infection.
• A tender, firm, enlarged thyroid
• Fever, tiredness and aching muscles
• Symptoms of hyperthyroidism: heart palpitations, shakiness, heat intolerance, sweating, anxiety, poor sleep and weight loss
• Later, symptoms of hypothyroidism

A painless variant exists (silent or painless thyroiditis), but that is a different, autoimmune condition, related to postpartum thyroiditis.

How it is diagnosed

1. Examination: a tender, firm thyroid in someone with neck pain and a recent viral illness is very suggestive.
2. Thyroid blood tests: high free T4 and T3 with a suppressed TSH in the early phase.
3. Inflammation markers: ESR is typically very high, often over 50 mm/hour, and CRP is raised.
4. Radioactive iodine uptake scan: uptake is very low because the damaged gland is not making hormone. This is the key test that separates thyroiditis from Graves' disease, where uptake is high.
5. Thyroid ultrasound: shows patchy, poorly defined areas with low blood flow.
6. Thyroid antibodies: usually negative or only mildly positive.

Conditions that look similar

Treatment

There is no treatment that speeds up the healing of the gland. Treatment controls symptoms through each phase.

Pain and inflammation

• NSAIDs such as ibuprofen or naproxen help mild to moderate pain. Follow the label dose and check with a doctor if you have kidney problems, stomach ulcers or take blood thinners.
• Prednisone (a steroid) is used for severe pain or when NSAIDs fail. Pain often improves within 1 to 2 days. The dose is tapered over 4 to 8 weeks, and pain sometimes returns as it is reduced.

Overactive phase

Beta-blockers such as propranolol control palpitations, tremor and anxiety. Antithyroid drugs (methimazole, propylthiouracil) do not help, because the gland is not overproducing hormone. It is leaking stored hormone.

Underactive phase

Mild, short-lived hypothyroidism often needs no treatment. If symptoms are troublesome or TSH is high, levothyroxine may be given for a few months and then stopped to see whether the gland has recovered.

Follow-up

Thyroid blood tests are usually repeated every 4 to 6 weeks until levels are normal, then at intervals to catch late hypothyroidism.

Outlook

Most people recover completely within 6 to 18 months. Relapse within the first year happens in roughly 1 in 5 people, often when steroids are tapered. Recurrence years later is uncommon. The main long-term issue is permanent hypothyroidism in a minority, which is easily treated with a daily tablet.

Frequently asked questions

What are the phases of subacute thyroiditis?

There are three typical phases. First, a thyrotoxic phase of 3 to 6 weeks with neck pain and an overactive thyroid. Second, a hypothyroid phase lasting weeks to months as hormone stores run out. Third, recovery, usually within 6 to 18 months, when thyroid function returns to normal.

What causes subacute thyroiditis?

It is thought to be caused by a viral infection, because it usually follows a cold, flu or other upper respiratory illness by a few weeks and is more common in summer and autumn. Cases have also followed COVID-19 and, rarely, vaccination. People with certain genetic HLA types are more prone to it.

How long does subacute thyroiditis last?

Pain usually settles within weeks to 2 months with treatment. The whole course, including any underactive phase, usually ends within 6 to 18 months. About 1 in 10 people have a permanently underactive thyroid afterward.

Is subacute thyroiditis serious?

It is painful and unpleasant but rarely dangerous. Complications such as severe heart rhythm problems are uncommon, mostly in older people with heart disease. Most people recover fully, and those left with low thyroid function do well on levothyroxine.

Can subacute thyroiditis come back?

It relapses in up to about 20% of people in the first months, often as steroids are reduced, and this is managed by restarting or slowing the taper. A true second episode years later is rare, occurring in only a small percentage of people.