Subacute and Painless Thyroiditis
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Direct answer
Subacute thyroiditis, also called de Quervain or granulomatous thyroiditis, is a painful, self-limiting inflammation of the thyroid that often follows a viral illness. It causes a triphasic course of thyrotoxicosis, then hypothyroidism, then recovery, with a raised ESR and very low radioiodine uptake. Painless thyroiditis has the same low-uptake pattern but no pain, and its ESR is normal.
What you must remember
- Pain: a tender thyroid, often radiating to the jaw or ear, with fever in the acute phase of subacute thyroiditis.
- ESR: markedly raised in subacute thyroiditis and normal in painless thyroiditis.
- Radioiodine uptake: very low in both, which distinguishes them from Graves disease.
- Triphasic course: a thyrotoxic phase lasting several weeks, a hypothyroid phase, then recovery over months.
- Treatment: NSAIDs or aspirin and beta-blockers, with prednisolone for severe pain; antithyroid drugs do not help.
- Painless causes: postpartum thyroiditis, lithium, amiodarone, interferon-alpha and immune checkpoint inhibitors.
- Histology: giant cell granulomas in subacute disease and lymphocytic infiltrate in painless disease.
A painful neck and a racing pulse
A 38-year-old woman has a week of neck pain radiating to the jaw, fever of 38.2 degrees and palpitations, with a tender, enlarged thyroid. Her TSH is undetectable, free thyroxine is high and ESR is 90 mm/hour.
- Confirm the low-uptake state. Radioiodine uptake at 24 hours is only about 2 per cent, which confirms a low-uptake state.
- Treat the symptoms. An NSAID is given for pain and a beta-blocker for palpitations.
- Withhold antithyroid drugs. They are not started, because the gland is not synthesising excess hormone.
- Anticipate the hypothyroid phase. Over the next weeks the thyrotoxicosis resolves and she enters a hypothyroid phase with fatigue and a raised TSH.
- Use levothyroxine selectively. It is given only if symptoms are significant, since the hypothyroid phase is usually temporary.
- Follow the recovery. Recovery is expected over several months, and thyroid function is checked at intervals.
Compared with Graves disease, the lack of diffuse uptake and the presence of pain steer the diagnosis, and the course is the reason the phases should be anticipated rather than treated as separate illnesses.
Where the exam tries to catch you
Thyroiditis questions turn on the mechanism behind the thyrotoxicosis.
- Trap: using antithyroid drugs or radioiodine for low-uptake thyrotoxicosis. Correct: the hormone leaks from damaged follicles rather than being made in excess, so antithyroid drugs fail and radioiodine has no target.
- Trap: confusing painless thyroiditis with Graves disease. Correct: Graves is also painless, but it shows high uptake and stimulating antibodies.
- Trap: assuming every low-uptake thyrotoxicosis is thyroiditis. Correct: factitious thyroxine ingestion and struma ovarii also cause low uptake, so the clinical history and ESR help.
- Trap: forgetting postpartum thyroiditis. Correct: it is the painless form examiners test most often, and it occurs within the first year after delivery.
Frequently asked questions
What is the triphasic course in subacute thyroiditis?
The triphasic course in subacute thyroiditis begins with a thyrotoxic phase caused by release of stored hormone, followed by a hypothyroid phase as the gland is depleted. Recovery to normal function usually occurs over several months. Not every patient passes through all three phases.
Why are antithyroid drugs not useful in subacute thyroiditis?
Antithyroid drugs are not useful in subacute thyroiditis because the thyrotoxicosis results from release of preformed hormone, not from excess synthesis. Drugs that block hormone synthesis therefore have no effect. Symptomatic control with beta-blockers and anti-inflammatory treatment is preferred.
What distinguishes subacute from painless thyroiditis on investigation?
ESR distinguishes the two conditions: it is markedly raised in subacute thyroiditis and normal in painless thyroiditis. Both show very low radioiodine uptake. Clinical pain and tenderness of the thyroid point toward subacute disease.
Which drugs commonly cause painless thyroiditis?
Lithium, amiodarone, interferon-alpha and immune checkpoint inhibitors commonly cause painless thyroiditis-type thyrotoxicosis. Medication history is therefore essential in any patient with low-uptake thyrotoxicosis. Stopping the drug is considered, depending on the indication.
What radioiodine uptake pattern is seen in painless thyroiditis?
Painless thyroiditis shows very low radioiodine uptake because the gland is not actively synthesising hormone. This contrasts with the diffusely high uptake of Graves disease. The pattern helps distinguish the two causes of thyrotoxicosis.