Unethical human experimentation in the United States
In 1953, the AEC ran several studies at the University of Iowa on the health effects of radioactive iodine in newborns and pregnant women. In one study, researchers gave pregnant women from of iodine-131, in order to study the women's aborted embryos in an attempt to discover at what stage, and to what extent, radioactive iodine crosses the placental barrier. In another study, they gave 25 newborn babies (who were under 36 hours old and weighed from ) iodine-131, either by oral administration or through an injection, so that they could measure the amount of iodine in their thyroid glands, as iodine would go to that gland.
Iodine
Iodine is an essential element for life and, at atomic number "Z" = 53, is the heaviest element commonly needed by living organisms. (Lanthanum and the other lanthanides, as well as tungsten with "Z" = 74, are used by a few microorganisms.) It is required for the synthesis of the growth-regulating thyroid hormones thyroxine and triiodothyronine (T and T respectively, named after their number of iodine atoms). A deficiency of iodine leads to decreased production of T and T and a concomitant enlargement of the thyroid tissue in an attempt to obtain more iodine, causing the disease known as simple goitre. The major form of thyroid hormone in the blood is thyroxine (T), which has a longer half-life than T. In humans, the ratio of T to T released into the blood is between 14:1 and 20:1. T is converted to the active T (three to four times more potent than T) within cells by deiodinases (5'-iodinase). These are further processed by decarboxylation and deiodination to produce iodothyronamine (Ta) and thyronamine (Ta'). All three isoforms of the deiodinases are selenium-containing enzymes; thus dietary selenium is essential for T production.