Iodine deficiency causes goitre, hypothyroidism, retarded physical development and impaired mental function, increased rate of spontaneous abortion and stillbirth, neurological cretinism, including deaf mutism and myxoedematous cretinism, dwarfism and severe mental retardation. It is the most common cause of preventable mental defect in the world today.
WHO estimated in 1990 that there were one billion people at risk of iodine deficiency disorders in developing countries. 190 million suffered from goitre and 20 million from mental defects due to iodine deficiency. Of these, more than 3 million were overt cretins. In 1997, 60% of the world's edible salt was iodized to combat the deficiency.
A 1995 survey of infants in China revealed that 35% to 65% had iodine deficiencies. A third of the global 1.6 billion iodine deficiency cases are in China. In 1997 in Georgia there was a widespread iodine deficiency and the 50,000 babies born there will be intellectually duller than normal by 10 IQ points.
Of the many disabling conditions that come massively in the way of human development, the endemic deficiency in iodine is second to none, in the severity of its consequences coupled with the spread of its prevalence. In some areas of the world 4 to 15% of the newborn infants are condemned to the destruction of their mental and physical health.
Iodine may be one of the potential culprits in the dramatic surge in diagnoses of Hashimoto’s thyroiditis, also known as autoimmune thyroiditis or chronic lymphocytic thyroiditis, which has occurred in recent years.