Iodine pill. A seaweed (kelp) pill containing the element iodine. Iodine is essential for the formation of thyroid hormones which control the body's rate of metabolism, growth and development. Some 100-300 milligrams of iodine are needed daily. Vegetable food and livestock grown in lime- stone areas may lack iodine. An iodine shortage may be overcome by eating bread or salt enriched with iodide. Iodine deficiency may lead to goitre (enlarged thyroid gland) or underactive thyroid gland. In the newborn it can lead to cretinism. Iodine pills may be given to people who have been contaminated with radioactive iodine, as this reduces the absorption of radioactive iodine.