Lugol's Solution-Induced Painless Thyroiditis

In 2014, a 59-year-old woman was prescribed Lugol's solution for menopausal symptoms and subsequently developed painless thyroiditis, characterized by fatigue, hair loss, and significant weight loss without thyroid pain. Laboratory tests revealed suppressed TSH and elevated free T4 levels, which later spontaneously normalized, although TSH remained low. Methimazole treatment caused TSH to rise sharply and was discontinued, leading to the patient's eventual return to a euthyroid state. This case, reported in 2017, is notable as a unique instance of Lugol's solution-induced painless thyroiditis, highlighting that while Lugol's solution is typically used short-term for thyroidectomy preparation in Graves' disease and severe thyrotoxicosis, its prolonged off-label use can lead to thyroid dysfunction, including both hypothyroidism and thyrotoxicosis, especially in glands with underlying pathology.