Iodine is a nonmetallic element that you need in trace amounts for the synthesis of thyroid hormones. Most of the Earth's iodine is found in its oceans, with smaller amounts distributed unevenly in soils. In 2008, the World Health Organization reported that iodine deficiency affects nearly 1 in 3 individuals globally. The amino acid tyrosine is also required for synthesizing thyroid hormones. However, unlike iodine, which must be obtained from your diet, tyrosine can be manufactured in your body from phenylalanine, another amino acid. Check with your physician before taking either iodine or tyrosine supplements.
Your thyroid gland is located in the front of your neck, just beneath your Adam's apple. This important organ is responsible for manufacturing and secreting thyroid hormones -- triiodothyronine, or T3, and thyroxine, or T4 -- which exert wide-ranging metabolic effects in your tissues. The cells in your thyroid are capable of "trapping" iodine ions from your bloodstream and attaching them to tyrosine molecules to produce T3 and T4, which are stored in your thyroid gland until your body needs them. T3 is the most active thyroid hormone in your body.
According to "The Merck Manual of Diagnosis and Therapy," thyroid hormones act on nearly every tissue and organ in your body. By attaching to receptors in your cells, thyroid hormones regulate the expression of your genes and alter the production of many cellular products. Thyroid hormones are required for growth and brain development in fetuses and newborn infants, and they are needed at all ages for protein, carbohydrate and fat metabolism.
A lack of dietary iodine or diseases of your thyroid can interfere with T3 and T4 production. Depending on your age, deficiency of thyroid hormones -- a condition called hypothyroidism -- can cause slowed metabolism, weight gain, delayed growth and development, poor mental function, depression, digestive disorders, menstrual irregularities and heart failure. The Linus Pauling Institute at Oregon State University reports that iodine deficiency is the most common cause of preventable brain damage in the world.
Recommended dietary allowances for iodine vary from 110 mcg daily for infants to 290 mcg daily for nursing mothers. Good food sources of iodine include fish, such as cod, perch and haddock, and sea vegetables, such as kelp. Iodized salt contains about 75 mcg of iodine per gram of salt. Although it is not necessary to supplement with tyrosine if you consume a balanced diet, the University of Maryland Medical Center suggests taking 500 mg of tyrosine 2 or 3 times daily to support thyroid function. However, if you are taking a thyroid medication, if you have high blood pressure or if you suffer from mania, you should not take tyrosine without your doctor's advice.