Abstract
Autoimmune thyroid disease (AITD) encompasses a spectrum of conditions ranging from Graves' disease (GD) to Hashimoto's thyroiditis (HT). These conditions often coexist with other autoimmune diseases (AIDs). This case describes a young woman in her 20s who transitioned from GD to HT during her first pregnancy, while having another coexisting AID, Sjogren's syndrome (SS). AITD and SS are recognized as the most common polyautoimmune diseases, sharing many common pathophysiological characteristics such as the presence of lymphocytic infiltrates, similar expressions of the human leukocyte antigen molecules, and predisposing environmental factors. This case underscores the importance for physicians to be vigilant regarding the possibility of changing antibodies in AITD and the potential for concurrent AIDs in a single individual. It highlights the need for screening such patients for comprehensive management.