- Clinical science
Subacute thyroiditis refers to a transient patchy inflammation of the thyroid gland that is associated either with granuloma formation (subacute granulomatous thyroiditis) or lymphocytic infiltration (subacute lymphocytic thyroiditis). While subacute granulomatous thyroiditis usually occurs after a viral upper respiratory tract infection, subacute lymphocytic thyroiditis occurs either during the postpartum period, in association with other autoimmune diseases, or as a side effect of certain drugs. Both forms of subacute thyroiditis are more common among women and are characterized by a triphasic clinical course that classically transitions from hyperthyroidism to hypothyroidism, before returning to a euthyroid phase. During the thyrotoxic phase, patients usually complain of fever, malaise, and goiter, which is tender in subacute granulomatous thyroiditis and painless in subacute lymphocytic thyroiditis. Diagnosis is confirmed by a combination of raised ESR and decreased iodine uptake in a radioiodine uptake study. During the thyrotoxic phase, beta blockers may be used to control the symptoms of thyrotoxicosis, and NSAIDs may be used to control pain among patients with subacute granulomatous thyroiditis. Small doses of levothyroxine may be considered during the hypothyroid phase. As spontaneous remission is seen in about 80% of cases, symptomatic treatment is sufficient in most cases.
- Sex: ♀ > ♂ (3:1)
- Peak incidence: 30–50 years
Epidemiological data refers to the US, unless otherwise specified.
Subacute thyroiditis is characterized by transient patchy inflammation of the thyroid gland (transient thyroiditis). Depending on the underlying cause, one of two types of histological changes are seen:
- Viral infections: mumps virus, coxsackie virus, influenza virus, echovirus, adenovirus
- Mycobacterial infections
- Drugs: α-interferon, lithium, amiodarone, interleukin-2, tyrosine kinase inhibitors
- Autoimmune disease
- Affects approx. 5% of women and usually arises during the 1st year after delivery
- Most prevalent in women with type 1 diabetes mellitus.
- Lasts 2–8 weeks
- Caused by damage to follicular cells and the release of pre-formed colloid (stored thyroid hormones)
- Hypothyroid phase
- Euthyroid phase: Thyroid function recovers and pathological changes are no longer visible in the thyroid gland.
The disease is self-limiting in most cases but a few patients may experience relapses, and permanent hypothyroidism occurs in ∼ 15% of cases!
- Possible history of upper respiratory tract infections a few weeks prior to the onset of subacute thyroiditis
- Painful, diffuse, firm goiter, jaw pain
- Fever and/or malaise may be present.
- Features of followed by features of
- Thyroid function tests
- Confirmatory test
- Thyroid autoantibodies are absent or appear in low titers.
- Ultrasound: thyroid with poorly defined hypoechoic regions and decreased vascularity, giving rise to a cobblestone appearance
- Histologic features :
- Thyrotoxic phase
- Hypothyroid phase: : levothyroxine
Antithyroid drugs should not be administered in the thyrotoxic phase of subacute thyroiditis!References: