Spontaneous remission of pendulum swinging thyroid disease in Down syndrome.

Rare patients who have both TSH receptor-stimulating and -blocking antibodies can switch between hyperthyroidism and hypothyroidism or vice versa during treatment with antithyroid drugs or thyroxine. Metamorphic thyroid autoimmunity is more common in Down syndrome. Switching between hyperthyroidism and hypothyroidism and back again is less commonly reported. Definitive treatment such as radioactive iodine or thyroidectomy are usually recommended. Prolonged remission was achieved off all medication, without recourse to definitive treatments.