["Block and replace" of sodium levothyroxine therapy]. / "Block and replace" della terapia con levotiroxina sodica.

We present the case of a 65 years old patient with Graves disease associated with hyperthyroidism and a medical history of bipolar disorder treated with lithium. Hyperthyroidism was initially treated with high-dose methimazole monotherapy and later the patient developed overt hypothyroidism (clinical and biochemical), but without remission of the underlying autoimmune disease. A "block and replace" therapeutic regimen was then started with reduced methimazole doses in combination with levothyroxine, which resulted in a short time in normalization of the hormonal profile and significant improvement of the clinical picture. Therefore, the "block and replace" regimen represents a valid therapeutic alternative to anti-thyroid drugs monotherapy in the treatment of hyperthyroidism due to Graves disease in selected cases.