What is the clinical course of subacute thyroiditis?

Updated: Mar 23, 2021
  • Author: Stephanie L Lee, MD, PhD; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Although the etiology appears to be different for the three subtypes, the clinical courses are the same. High thyroid hormone levels result from the destruction of the thyroid follicle and the release of preformed thyroid hormone into the circulation, with thyrotoxicosis consequently developing. (The high thyroid hormone levels are not a function of new thyroid hormone synthesis and secretion.) This phase lasts 4-10 weeks. (See Pathophysiology and Etiology.)

The thyrotoxic phase undergoes spontaneous remission in 4-8 weeks. At this time, the thyroid is depleted of colloid and is now incapable of producing thyroid hormone, resulting in hypothyroidism. The hypothyroid phase may last up to 2 months. Often, the hypothyroidism is mild, and no thyroid hormone therapy is required unless the patient has signs or symptoms of hypothyroidism. As the follicles regenerate, the euthyroid state is restored. Depending on the etiology, 90-95% of patients return to normal thyroid function. (See Prognosis.)

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