Iodine is an element that is needed for the production of thyroid hormone. The body does not make iodine, so it is an essential part of your diet. Iodine is found in various foods, such as fish, vegetables and iodized salt. If you do not have enough iodine in your body, you cannot make enough thyroid hormone. Thus, iodine deficiency can lead to enlargement of the thyroid, hypothyroidism and to mental retardation in infants and children whose mothers were iodine deficient during pregnancy.

Hypothyroidism slows metabolism, causing such symptoms as fatigue, weight gain, weakness, increased cold sensitivity, constipation, dry skin, and depressed mood. Your hair and nails may be thin and brittle and, if you are female, your menstrual cycle may become abnormal. If Left untreated, your skin may swell and thicken, your eyes may seem to protrude, mental function may decline, and you may ultimately lapse into a coma.
http://healthful.com.ng/the-future-of-iodine-deficiency/