Some of the elements in the periodic table show up regularly in everyday language, such as, "good as gold," a "mercurial wit," or a "platinum" credit card.
On the other hand, most elements pass almost unnoticed.
Iodine is a good example. Perhaps if you work in health care you use compounds containing iodine as an antiseptic; otherwise, you are only reminded of iodine if you happen to look at the very small print on a container of iodized salt: "Contains iodine, an essential nutrient."
Iodine, atomic number 53, was discovered in 1811, and then named in 1813 by Gay-Lussac who used the Greek word iodis for "violet-colored," which is what is seen when the purple-black mass of iodine sublimes to form a purple-violet gas.
Despite its relative rarity, iodine plays a central role in the growth and development of vertebrates.
Very early in the history of life on Earth, organisms evolved the capability to collect iodine from the environment and bind it to a protein.
Ever since, iodine-based proteins (iodothyronines) have played a central role as regulatory molecules in vertebrate physical development, as well as the development of the newborn's nervous system and supporting adult brain function. (Schroeder, 2014)
The modern Sea Squirt is a member of an ancient family of organisms called urochrodates that appeared about 540 million years ago. Like its extinct ancestors, the Sea Squirt is able to use iodide collected from its marine habitat to synthesize thyroxinine. Further cell chemical processes then transform the thyroxinine into a new molecule triiodothyronine in which the iodine is more concentrated.
These two molecules, thyroxinine and triiodothyronine synthesized by the early relatives of the modern Sea Squirt, are the same molecules identified as T3 and T4 synthesized in the human thyroid. (Dumont, 2016)
To thrive as living organisms both Sea Squirts and humans share a common task: to produce iodine-based molecules, release them into the circulatory system so that they reach every cell in the body carrying messages that regulate the beginning, the speeding up, the slowing down or the ending of the many processes related to physical and neural development.
In humans, the secretion of T3 and T4 into the blood stream in specific levels regulates breathing, heart rate, the central and peripheral nervous system, body weight, muscle strength, menstrual cycles, body temperature, cholesterol levels. If the levels of the T3 and T4 are too low the individual may be anxious, irritable, sensitive to high temperatures. While if the levels are too high, the individual may suffer from sleeplessness, sensitivity to cold, joint and muscle pain. More information is here. Recent studies suggest that T4 plays a greater role in brain development than had been previously thought. (Schroeder, 2014)
In humans, the machinery in the thyroid gland for synthesizing the T3 and T4 molecules is initiated by a small structure in the brain called the hypothalamus where the endocrine system and the nervous system are linked. If the blood concentration of T3 and T4 are too high or too low, the hypothalamus signals the pituitary gland which responds by signaling the thyroid to produce more or less of the T3 and T4 molecules. You can read the details of the process here.
The key fact is that the thyroid and its effectiveness is utterly dependent on the ability of the body to acquire an adequate supply of iodine from the environment.
While humans live everywhere, large inhabited areas of earth have little or no iodine in the soil.
According to the World Health Organization (WHO), people who live in areas that do not have sufficient iodine in the environment are at risk for disorders like goiter (enlarged thyroid) as well as being at risk for mental retardation and varying degrees of physical and mental developmental problems, including cretinism. About one-third of Earth's population live in such environments and, as a consequence, there are about 740 million people who suffer from iodine-related mental and physical problems.
In the U.S. a region that included the upper Midwest, Appalachia, and the northwestern states was once known as the goiter belt because it was common to see individuals with large growths on their throats. When there is an insufficient amount of iodine, the follicles that synthesize T3 and T4 become larger. Long-term iodine deficiency may result in both physical and neurological difficulties as well as a disfiguringly-large and permanent growth on the neck.
Medical screenings given to World War 1 draftees showed that perhaps one-third of young men from the goiter belt had the tell-tale growths.
In contrast, South Carolina recruits almost never suffered from goiter because fruits and vegetables grown in South Carolina soils are rich in iodine in the form of iodide.
To capitalize on this fact, the state Natural Resources Commission began a campaign in the early 1930s "to advertise the high iodine levels found in fruits and vegetables grown in the state. Even South Carolina milk was promoted as containing extraordinarily high levels of iodine. Promotional tracts sought to expand the national market for South Carolina product by warning Midwestern and West Coast residents of the consequences of iodine deficiency for the young, including enlarged thyroid glands, mental and physical birth defects, and even sterility. The campaign placed the motto "Iodine" on South Carolina automobile license plates in 1930, then expanded the phrase in subsequent years to "The Iodine State" and "The Iodine Products State." (South Carolina Encyclopedia)
One of the last remaining evidences of this campaign is found in a local radio and tv station's call letters WIS standing for the motto "Wonderful Iodine State."
For a brief moment, iodine got some respect.
Brody, Bridget, MD. (2016). Thyroid Gland, How It Functions, Symptoms of Hyperthyroidism and Hypothyriodism. endocrineweb.com
Dumont, Jacques and Robert Opitz, et.al. (2016). Ontogeny, Anatomy, Metabolism and Physiology of the Thyroid. Thyroid Disease Manager. R
Schroeder, A. C., & Privalsky, M. L. (2014). Thyroid Hormones, T3 and T4, in the Brain. Frontiers in Endocrinology, 5, 40. http://doi.org/10.3389/fendo.2014.00040
Edgar, Walter D. (ed). “Iodine” in The South Carolina Encyclopedia. Retrieved 10/20/2016 from http://www.scencyclopedia.org/index.htm
Note: In the U.S. large salt producers began to add potassium or sodium iodide to their salt in the 1920s. Since the 1940s nearly all the salt consumed in the U.S. is iodized.
Dr. John Holton
Dr. John Holton joined the S²TEM Centers SC in July of 2013, as a research associate with an emphasis on the STEM literature including state and local STEM plans from around the nation.