[Recognise of iodine effect on thyroid diseases and metabolism]

Iodine is an essential trace element for human and an antioxidant. It not only participates in the synthesis of thyroid hormone, but also plays a role in metabolic diseases. Previous studies mainly focused on the effect of iodine on thyroid diseases, but ignored the effect on metabolism. After the implementation of the universal salt iodization (USI) of China, the possible consequences of excessive iodine were emphasized while the harm of iodine deficiency was forgetten. The paper re-examines the effects of iodine nutrition on thyroid diseases and metabolism. Iodine deficiency can lead to an increased risk of iodine deficiency disorders and thyroid diseases, and increase prevalence of metabolic syndrome and its components. Moderate iodine excess is beneficial to metabolism, but it can increase the risk of hyperthyroidism and subclinical hypothyroidism. The average urinary iodine concentration in 100-299 μg/L is the appropriate iodine nutrition state. According to the present iodized content of salt in China, iodized salt is an economical and effective way to ensure adequate iodine nutrition.