Iodine deficiency is an important public health problem both in our country and around the world. Iodine deficiency and the health problems it causes, to the large-scale struggle involving health and aid organizations such as the World Health Organization, United Nations Children's Fund (UNICEF), to accept 21 October as the Global Day for the Prevention of Iodine Deficiency Disorders to raise awareness, to carry out activities in this regard. however, it is still common. Iodine deficiency is seen in 40% of the world population, especially in rural areas. It affects people of all age groups, including infants, pregnant women and children. Fighting iodine deficiency has become the policy of states. In this regard, it has been decided to iodize table salt worldwide and in our country, and table salt has been iodized. In our country, the necessary legal regulations for the mandatory iodization of all table salt were completed in July 1999 and the use of iodized salt has been expanded since the 2000s. At the end of these struggles, iodine deficiency is slightly reduced compared to the old data, but its frequency is still high. In this review, iodine, the causes of iodine deficiency, its incidence, how it is evaluated, the health problems it causes, its treatment and struggle are mentioned.