[Thyroid dysfunction: interactions between genetic and environmental conditions]

Thyroid dysfunction (TD) is a very common entity in clinical practice nowadays. Prevalence may be underestimated because of the limitations of epidemiological studies. There are mainly genetic and environmental factors that interact on thyroid function. Genetic factors are extensively described in literature but molecular advance on the field may change older classifications based on B-cell or T-cell mediated disorders. The dominant pattern of inheritance makes family predisposition a relevant question in patient medical history but clinical research show that immune system is not enough to cause overt dysfunction. The role of environmental factors generates debate on medical literature. Some classic factors as iodine intake are well characterized but others as fetal microhimerism or new antineoplastic agents are less known. A review of medical literature on thyroid dysfunction has been performed and genetic and environmental factors are described in this article.