[Physiopathology of iodine: current interest of its measurement in biological fluids].

Iodine plays a central role in thyroid physiology, being both a major constituent of thyroid hormones and a regulator of thyroid gland functions. Iodine intakes considerably vary according to subjects. Inappropriate iodine intakes are worrying in term of public health regarding iodine deficiency (western world currently is not exempt) and regarding the frequency of iatrogen iodine overloads. Iodine disorders induce a biological and/or clinical expression of thyroid dysfunction, and in some cases can disclose pre-existent thyroid abnormalities. Determination of serum and urine iodine levels is an useful marker in the biological investigation of the thyroid function, can contribute to undertake an appropriate therapeutics and follow its efficacy.