Can Quetiapine-Induced Hypothyroidism be Reversible Without Quetiapine Discontinuation?

Recent clinical trials and case reports have recorded dose-related thyroid function test abnormalities during quetiapine treatment usually requiring drug discontinuation or initiation of thyroid replacement therapy. The authors highlight the potential reversibility of quetiapine-induced hypothyroidism without quetiapine discontinuation in 2 in-patients (a 51-year-old schizophrenic woman and a 46-year-old bipolar man) to which quetiapine (300 and 350 mg/d, respectively) was administered. Both patients had a negative personal and family history of thyroid dysfunction. Significant decreases in T4/free T4 levels and a marked elevation in thyroid-stimulating hormone level were recorded without any clinical signs of hypothyroidism 3 weeks after quetiapine initiation. Antithyroid antibody titers remained within reference range. Thyroid function tests returned to normal 6 weeks after quetiapine initiation, although quetiapine was continued at the same daily dose without thyroid replacement therapy. These are the first cases reporting spontaneous resolution of quetiapine-induced hypothyroidism without quetiapine discontinuation. We suggest careful thyroid monitoring for patients initiating quetiapine. However, physicians can wait in cases of quetiapine-induced hypothyroidism if a close laboratory monitoring is available because thyroid dysregulation may soon resolve.