Painless thyroiditis is characterized by focal lymphocytic infiltration within the thyroid and presents as transient, reversible destruction of thyroid follicles. It can occur at any age, with a higher prevalence in females compared to males. Patients typically exhibit mild, diffuse thyroid enlargement with a firm texture and no localized tenderness. The changes in thyroid function resemble those seen in subacute thyroiditis, with a clinical course that includes thyrotoxic, hypothyroid, and recovery phases. The thyrotoxicosis in this condition arises from the release of thyroid hormones into the bloodstream due to autoimmune inflammation and follicular destruction. Permanent hypothyroidism persists in approximately 20% of cases, and 10% of patients experience recurrence.
Postpartum thyroiditis (PPT) is considered a variant of painless thyroiditis and occurs within the first year after childbirth. The presence of TPOAb positivity is a risk factor for developing PPT. The typical clinical course includes thyrotoxic, hypothyroid, and recovery phases, accounting for 43% of PPT cases. Isolated thyrotoxicosis is observed in 46% of cases, while isolated hypothyroidism occurs in 11% of cases. Permanent hypothyroidism persists in about 20% of patients.