Unilateral Graves' Disease: A Rare Case of Isolated Left-Lobe Hyperthyroidism in an Adolescent Female

Graves' disease is an autoimmune disorder that causes hyperthyroidism and typically involves both thyroid lobes. Unilateral Graves' disease (UGD) is a rare variant characterized by hyperfunction of a single thyroid lobe. The pathophysiology underlying this asymmetric involvement remains unclear, and several hypotheses have been proposed. We report a rare case of isolated left-lobe hyperthyroidism due to UGD in an adolescent female, incidentally detected during routine biochemical evaluation. Further investigations, including thyroid scintigraphy, confirmed unilateral disease. Despite treatment with high-dose antithyroid drugs, sustained biochemical control could not be achieved, prompting counseling regarding early definitive treatment options. Accurate differentiation of UGD from toxic adenoma and toxic multinodular goiter is essential, as management strategies and recurrence risks differ. This case highlights the diagnostic and therapeutic challenges associated with UGD and underscores the importance of individualized management guided by available literature and expert consensus.