Iodine condition seems to occur mainly in people over forty, and the risk appears higher when iodine deficiency is severe and the initial rise in iodine intake is high. In areas where there is little iodine in the diet, typically remote inland areas and semi-arid equatorial climates where no marine foods are eaten, iodine deficiency gives rise to hypothyroidism, symptoms of which are extreme fatigue, goitre, mental slowing, depression, weight gain, and low basal body temperatures. Iodine deficiency is the leading cause of preventable intellectual disability, a result that occurs primarily when babies or small children are rendered hypothyroidic by a
Vitamin A deficiency conjunctiva, known as Bitot's spots, can be seen. ; Imtiaz's sign is the earliest ocular sign of VAD. Conjunctival epithelial defects occur around lateral aspect of the limbus in the subclinical stage of VAD. These conjunctival epithelial defects are not visible on a biomicroscope, but they take up black stain and become readily visible after instillation of kajal (surma); this is called "Imtiaz's sign". VAD can also lead to impaired immune function, cancer, and birth defects. Vitamin A deficiency is one of several hypovitaminoses implicated in follicular hyperkeratosis. Night blindness is the difficulty for the eyes to adjust to dim