SARS-CoV-2 infection induces the dysfunction of many organs including the thyroid gland through the role of ACE2 receptors as well as the consequences of the cytokine storm. Thyroid diseases such as subacute thyroidism, Graves' disease, thyrotoxicosis, and Hashimoto's thyroiditis have been documented in patients with SARS-CoV-2 infection. However, there are limited reports about the consequences of SARS-CoV-2 infection-related thyroid complications. We describe a case of man who was admitted to the emergency department due to repeated lower limb weakness since diagnosed with COVID-19. He had refractory hypokalemia and was treated with potassium replacement therapy for 2 months. However, the complaints continued. The patient has no history of thyroid disease, yet the laboratory result showed hyperthyroidism. Accordingly, he received oral thiamazole. As the laboratory parameters of the thyroid hormones improved, potassium levels returned to normal and the limb weakness stopped. This unusual thyroid complication should be considered in SARS-CoV-2 infection. The prompt diagnosis and appropriate therapy can reduce the burden of the disease.