Two cases are reported of women aged 18 and 36 years respectively who developed a typical picture of hyperthyroidism by Graves Basedow disease (primary hyperthyroidism, diffuse goiter with increased uptake, positive stimulating thyroid antibodies, exophthalmos). These women had taken drugs for obesity which were prepared by magistral formula and acquired by mail 8 and 9 months prior to diagnosis of the disease. The differential diagnosis is discussed which should be considered in a women with hyperthyroidism and the antecedent of ingestion of weight-reducer drugs as well as the orientative data of the different causes. Also, the possible role of these drugs as triggering factor for the autoimmune thyroid disease is discussed.