Iodine

The World Health Organisation has classified Australia as a mildly iodine deficient country. Most iodine is found in seafood or in iodine-fortified foods.
Iodine is required by our bodies for the synthesis of thyroid hormones T3 and T4, and is therefore essential for normal thyroid function. Not getting enough iodine in your diet may produce deficiency disorders, which can result in hypothyroidism, mental retardation, goiter, and abnormalities associated with growth and development.
If you suspect your iodine intake is low, ask your healthcare practitioner what is the best source for you.
http://www.vitalhealthzone.com/nutrition/minerals/iodine.html