[Fucus vesiculosus induced hyperthyroidism in a patient undergoing concomitant treatment with lithium].

INTRODUCTION Fucus vesiculosus is a marine alga rich in iodine, which is being used in alternative medicine as a laxative, diuretic, and as a complement for weight loss diets. CASE REPORT We report the case of a 60-year old male patient, diagnosed with bipolar disorder and under treatment with lithium concomitantly with a herbal preparation, including Fucus vesiculosus, as a laxative. He developed hyperthyroidism that remitted once the herbal preparation was withdrawn. CONCLUSION Fucus vesiculosus may cause hyperthyroidism given its high iodine content. Herbal preparations should be taken in account when treating a patient due to the possibility of adverse effects and interactions with other drugs.