Iodine has an atomic weight of 126.9 and is widely distributed in the crust surface as a halogen element. During the Ice Age, under the long-term influence of natural forces such as glaciers, floods and infiltration, iodine appeared in various geographical distributions, mainly distributed in the crust of coastal areas, and seafood such as kelp became the most common source of iodine.
Before the discovery of iodine, China first recorded the treatment of goiter with iodine-containing substances in the world. As early as 3600 BC, it was recorded in China's medical works that giving kelp and charred sponge to patients with thick neck (goiter) could reduce the volume of goiter. Ge Hong in Jin Dynasty recorded that "seaweed wine prescription" was used to treat "scabies", commonly known as coarse neck disease, and medically known as diffuse goiter. In the following centuries, famous physicians in history, including Hippocrates, Galen, Roger and Arnold of villanova, recorded cases that iodine-containing seafood could treat goiter.
Liu Yuanqing, an educator in China in the Ming Dynasty, included a fable about "big neck disease" in Xian Yi Compilation:
Nanqi is located in the valley around Shaanxi and Sichuan. The residents there seldom associate with outsiders. The water in Nanqi is sweet, but not good. Drinking this water all the year round will cause big neck disease. None of the residents of Nanqi has a big neck. One day, a man came from outside the mountain and caused a sensation in Nanqi. Residents of all ages came to watch. As they watched, they talked about the necks of outsiders:
Like many important discoveries in the history of science, the discovery of iodine is full of surprises.
Iodine was discovered by French chemist Bernard Courtois in 65438. At that time, courtois tried to extract sodium and potassium compounds from seaweed residue. The original intention of extracting these compounds is to find raw materials for making explosives. He accidentally added too much sulfuric acid to further treat the sample and purple smoke appeared. Smoke condenses on indoor metal objects and becomes solid iodine. Today, iodine mainly exists in the form of precipitation of sodium iodate (NaIO iodine 3) and sodium periodate (NaIO 4).
The irony of this matter is that courtois's original intention of doing this experiment is not to find a panacea for saving lives, but to help Napoleon solve the problem of insufficient raw materials for explosives: potassium nitrate is needed to make explosives, while in the previous method, potassium was extracted from wood ash, but at that time, wood was in short supply, and the coasts of Normandy and Brittany were rich in seaweed, so courtois tried to extract potassium carbonate from seaweed ash, and the above scene happened.
As a chemist, Cortez realized that he might have discovered a new substance. He conducted a series of experiments and found that this new substance combines well with phosphorus, hydrogen and some metals, but it is not easy to react with oxygen or carbon. In addition, he also found that this new substance will not decompose when mixed with ammonia. Unfortunately, however, during the Napoleonic period, France was in a state of war and the army was short of money, so courtois was not allowed to conduct further experiments to identify this new substance. He had to turn to another French chemist, De Somers. With the help of his son-in-law Clemente, De Somers made an in-depth study of this purple substance. "Cool Brother" thinks this is not enough. He sent back the samples to two other famous French chemists, Gay-Lussac and Andre Ampere. So the two groups that got the samples published their findings in meetings or magazines respectively, and they suspected that it was a new substance or an oxidation product. The laurel of finally determining that this is a new substance and naming it fell to Sir humphry davy, a British chemist. Ampere sent some samples to David, and David announced on18131210 that he had discovered a new substance called iodine (from Greek, meaning purple).
Eight years after iodine was found in seaweed, Swiss doctor J.F. Coindet found that burnt sponge and seaweed can treat goiter, thus inferring that iodine in seaweed may be an effective component. 18 19 years, his tincture iodine was tested in 150 patients with goiter, and the dose was 250mg/ day, which was successful: the goiter was obviously reduced within one week. And published his results in 1820.
From 65438 to 0850, French chemist Chatin studied the relationship between the prevalence of goiter and the concentration of iodine in soil, water and food. He also studied the effect of iodine supplementation on the prevalence of goiter. He observed: 1) goiter and cretinism (insufficient iodine intake in pregnant women leads to congenital hypothyroidism in infants) are rare in iodine-rich places; 2) But it is common in places with insufficient iodine; 3) Iodine supplementation can prevent goiter.
From 189 1 to 1892, British Medical Journal (BMJ) published a series of articles, which reported that thyroid extract was used to treat hypothyroidism. 1895, Bowman detected high concentration of iodine in thyroid gland, and proposed that thyroid extract can treat hypothyroidism precisely because it contains iodine. For the first time in human history, a substance can be found to treat diseases in such a "causal" way. The role of iodine is greatly exaggerated. In the following years, "iodine" became the magic medicine in the eyes of the public, and it was used in almost every disease in clinic: paralysis, diarrhea, scrofula, lacrimal fistula, spinal deformity, syphilis ...... so that Hungarian doctors won the Nobel Prize for discovering vitamin C later.
K and I here are potassium and iodine. 185 1 annual registration of iodine-containing preparations 10 species, 1956 became 1700 species.
1940, radish and Perloff published "drug treatment of hyperthyroidism" in the journal of endocrinology. At that time, taking iodine and X-rays alone had become the most routine treatment for hyperthyroidism.
The strongest public doubt about the magic of iodine comes from Koukl, a Swiss surgeon in the early 20th century. It is worth mentioning that Koukl won the 1909 Nobel Prize in Medicine for the improvement of thyroidectomy, which is the first and only Nobel Prize in the field of thyroid in history. In the second year after he won the prize, Koukl publicly reported that his body developed severe hyperthyroidism after taking iodine, and he further opposed the use of iodine preparations in any form of hyperthyroidism treatment. Because of the great fame that Nobel brought to Koukl, his "phobia" about iodine therapy may come at the right time. Many thyroid doctors are scrambling to give up using iodine to treat goiter. Because of Koukl's influence, clinicians are divided into two groups: the "iodine school" advocates the treatment of hyperthyroidism with iodine, unless the effect is not good, X-ray irradiation or surgery; "Surgical School" does not recommend iodine, but recommends surgery as the only treatment for hyperthyroidism. The influence is not limited to Europe, but also spread to the United States. Although there have been countless clinical evidences to prove the effectiveness of iodine alone in treating hyperthyroidism, the view that "surgery is the main treatment for hyperthyroidism" has also spread rapidly in the United States.
During the 100 years since the discovery of iodine, the clinical application of iodine was mainly based on experience and trial and error, and the concept of iodine as an essential trace element for human body was not established at all. 19 1 1 year, Gabriel Bertrand, a French biochemist, first put forward the concept of trace elements in human body, believing that trace elements in human body are necessary for basic physiological processes such as human growth. He first discovered oxidase in plants and found that manganese metal was indispensable to the function of oxidase. Based on Bertrand's theory of trace elements, David Marine, an American pathologist, conducted a large-scale experiment on trace elements in human body, which may be the first time or the last time in history. The experiment was conducted among school girls (10~ 18 years old) in Ohio for five years. Subjects must have no symptoms of goiter, and they are divided into control group (2305 people, without iodine supplementation) and experimental group (2 190 people, supplemented with iodized salt 4g/ year, equivalent to 60 times the recommended dose today! )。 After two and a half years of observation, 495 girls in the control group developed goiter (22%), but only 5 girls in the iodine supplementation group developed symptoms (0.2%), and another 0.5% girls developed iodine poisoning symptoms. Today, the importance of this experiment cannot be overestimated. It shows for the first time that a trace element is necessary for human physiology.
Based on Marin's experiment, iodized salt is generally accepted by the medical community and the public. Switzerland and the United States are the first countries in the world to promote iodized salt. For the United States, the Great Lakes, the Appalachian Mountains and the northwest of China are the high incidence areas of coarse neck disease, and the incidence rate of local children was as high as 26%~70%, so this area is also called the "goiter zone". In the late 1940s, the American Commission on Thyroid Epidemiology proposed a bill: compulsory iodized salt in all states, but in the end the bill failed to pass. At the state level, most States are promoting iodized salt. Since the 1950s, the proportion of iodized salt in the American market has been 70-76%.
Iodine is not only the raw material for the synthesis of thyroxine in vivo, but also necessary for the formation of fetal brain sheath in uterus and early postpartum. Especially during pregnancy and lactation, iodine deficiency is prone to occur. From the public health point of view, the large-scale goiter epidemic caused by iodine deficiency in most countries, including China, no longer exists, but iodine supplementation during pregnancy and lactation is still a serious public health problem. The World Health Organization recommends taking 250 micrograms of iodine every day during pregnancy and lactation. The guidelines of American Thyroid Association and Endocrine Association also suggest that vitamins during pregnancy should contain 150 micrograms of potassium iodide every day.
After the founding of People's Republic of China (PRC), China began to popularize iodized salt and formulated the iodine content standard of salt. National iodine nutrition monitoring and iodized salt quality testing were carried out, and China's iodized salt standards were formulated according to the test results. The latest national test was in 2005, and the results showed that the average urinary iodine in most provincial administrative regions was slightly higher than the appropriate level recommended by the World Health Organization, and a few provinces exceeded the standard, and 9 provinces were the appropriate level. At that time, all the experts involved in the investigation thought that the iodine content in edible salt should be slightly reduced. At the same time, experts also believe that the same amount of iodine supplementation should not be implemented nationwide, but should be specifically adjusted according to the local urine iodine value of each province or region to avoid iodine excess in some areas and iodine deficiency in some areas. Based on this, the country adjusted the iodine content standard of edible salt for the third time:
The joint report of the World Health Organization (WHO), the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) and the United Nations Children's Fund (UNICEF) recommends that the daily adequate iodine intake (RDA, AI, that is, the lower limit) is as follows:
It is generally believed that normal people have a very high tolerance to iodine, and various organizations and countries have different regulations on the maximum safe intake limit (UL) of iodine per day:
refer to
Guy E. Abraham, MD, "The History of Iodine in Medicine", original physician, 2006.
Angela M. Leung, "The history of iodine fortification and supplementation in the United States" Nutrients 2012,4, 1740- 1746.
The history of iodine. http://www.mnwelldir.org/