Iodine and goiter involution.

Iodine administration, although efficient in goiter treatment or prevention, is also responsible for adverse effects such as cell necrosis or thyroiditis. These two effects were reproduced in iodide-treated goitrous mice. Morphological observations strongly suggest that thyroid cell death results from an excessive production of free radicals, which initiates lipid peroxidation. This hypothesis is strengthened by the facts that the thyroidal concentration of malonic dialdehyde, a stable product of lipid peroxidation, is increased, and that necrosis is partially prevented by free radicals scavengers. Epithelial necrosis is associated to an inflammatory reaction. The infiltrate is mainly made of cells expressing class II molecules of major histocompatibility complex (macrophages and dendritic cells), but also of T lymphocytes. However, this inflammation, which varies among mouse strains, is transient and it is not amplified or maintained by administration of cytokines, IFN gamma or TNF alpha, known to induce class II expression on thyrocytes.