Thyroid hormones are essential for normal growth, development and functioning of both the brain and body. Lack of iodine results in deficiency of these hormones leading to a spectrum of disorders, collectively called iodine deficiency disorders (IDD) that include goitre, irreversible brain damage, birth defects, stillbirths, deafness, dumbness, squint, cretinism and various levels of physical and mental retardation. According to the World Health Organisation (WHO), iodine deficiency is the single most important cause of preventable brain damage or mental retardation worldwide. The most visible and easily recognizable sign of iodine deficiency is goitre. A goitre is an enlarged thyroid gland, which can range is size from an invisible swelling to a monstrous growth in the neck.
