Subacute granulomatous thyroiditis is often self-limiting and can result following a flu-like illness (e.g. viral infection).
Subacute granulomatous thyroiditis can present with jaw pain along with a tender thyroid. This is unique as most thyroid conditions involve a non-tender thyroid.
This disease may present as hyperthyroidism early in the course, proceeding to euthyroidism, and then becoming hypothyroidism. The hypothyroidism can be permanent in ~15% of cases.
Thyroid function tests (TFTs) should be performed to evaluate for T3/T4 and TSH levels. In the thyrotoxic phase, there are elevated levels of T3/T4 and thyroglobulin, with decreased levels of TSH. The TFTs change in the hypothyroid phase, which has decreased T3/T4 and increased TSH.
Erythrocyte sedimentation rate (ESR) is a common inflammatory marker. ESR is often elevated in these patients.
With a radioiodine uptake study, there is decreased uptake (<5%) in those with subacute thyroiditis. This is due to follicular cell damage being unable to take up the iodine. Also, as TSH secretion is initially suppressed during the thyrotoxicosis phase, this also impacts iodine uptake. Radioiodine uptake normalizes once TSH levels begin to rise during the hypothyroid phase.
On histology, granulomatous inflammation along with multinucleated giant cells is hallmark.
In the thyrotoxic phase of subacute thyroiditis, beta-blockers can control the symptoms of hyperthyroidism (e.g. palpitations or anxiety).
NSAIDs are helpful for pain management.
Antithyroid drugs (e.g. methimazole) are contraindicated and should not be administered during the thyrotoxic phase of subacute thyroiditis. As the thyroid tries to recover its follicular cells, ATDs can actually inhibit thyroid hormone synthesis.
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