Painless thyroiditis as a precursor to the relapse of Graves’ disease during remission

The clinical profile of Graves’ disease (GD) after painless thyroiditis (PT) is nearly exclusively known from case reports, but it has never been investigated in depth. This study investigated the clinical characteristics of 18 patients (4 men, 14 women), with a median age of 32(25−48) years who developed GD out of a total of 862 patients who were diagnosed with PT based on high free thyroxine, suppressed thyroid-stimulating hormone, negative receptor antibody, and low 123I-uptake (<5%). Additionally, we compared their clinical characteristics with 162 patients (39 men, 123 women), with a median age of 37 (7−71) years who had the new-onset GD. The patients who developed GD after PT included 12 (7.2%) of 167 patients who recovered from GD and 6 (1.1%) of 559 patients with chronic thyroiditis (p < 0.0001). Of the 18 patients who developed GD following PT, 12 (66.7%) already recovered from a previous bout of GD and developed PT after having discontinued medical treatment and 16 (88.9%) developed GD 4–29 months after PT. The 2-year remission rates for the 16 patients who developed GD up to 29 months after PT and for the new-onset GD patients were 56.3% and 24.7% (p = 0.0070) and the 4-year remission rates were 75.0% and 38.3% (p = 0.0045), respectively. The development of PT after GD recovery may become a risk factor for GD recurrence. Patients who developed GD immediately after PT had comparatively milder disease and appeared to achieve remission in a short time.