Characteristic course of thyroiditis (painless, postpartum, or subacute)

The initial thyroid inflammation damages thyroid follicles and activates proteolysis of the thyroglobulin stored within the follicles. The result is unregulated release of large amounts of T4 and T3 into the circulation and, therefore, hyperthyroidism. This state lasts only until the stores of thyroglobulin are exhausted because new hormone synthesis ceases. As the inflammation subsides, the thyroid follicles regenerate and thyroid hormone synthesis and secretion resume. There may be a transient period of hypothyroidism and increased TSH secretion before thyroid secretion becomes normal again. However, some patients have only a hyperthyroid or hypothyroid phase.