Dieticians Association of Australia Newsletter, March, 2000. The two main thyroid hormones, thyroxine and tri-iodothyronine, are synthesised from the amino acid tyrosine and from iodide. These two hormones regulate metabolic rate and promote growth and development throughout the body including the brain. If there is a deficiency of thyroid hormones in the blood, the thyroid gland enlarges and becomes what is known as goitre. Aside from resulting in goitre, iodine deficiency can lead to dry skin, hair loss, fatigue, and slowed reflexes.
Iodine deficiency is especially serious in the developing fetus and young child.
Lack of iodine is a major problem in developing countries and is considered to be the world's number one cause of preventable intellectual disability in children. Another group that may be at risk of iodine deficiency is vegetarians if they do not eat seafood. Instead they can get their iodine from iodised table salt, or seaweed. Iodised salt is the most common source of iodine in the Western Diet. An adult only requires approximately one teaspoonful of iodine throughout their life, so eating fish once a week will be enough to fill this requirement.