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Section XI: Medical Sciences (Including Physiology) 1 98th Indian Science Congress January 3-7, 2011, Chennai I PRESIDENTIAL ADDRESS President : Prof. Amar K. Chandra PRESIDENTIAL ADDRESS Thyroid Functions in Iodine Deficiency and Region Specific Environmental Goitrogens - their impact in life and society Prof. Amar K Chandra* Distinguish Scientists and Honorable Delegates from the Country and Abroad It is a great privilege and pride of mine to welcome you all in the inaugural session of the Medical Sciences (including Physiology) Section in the 98th Session of Indian Science Congress in about 350 years old city of Chennai, formerly called as Madras, the gateway to South India, and it is rich in the treasures of history from temples and shrines to forts and palaces. It is one of the largest metro cities of the country and is the major trade centre of India. The venue is at SRM University which is about 25 years old that has set outstanding standards in higher education, especially in the field of Science, Technology, Medicine and Management and thus greatly involved in shaping the higher education as dreamt by our great leaders. The topic of today’s presidential address focuses on a micronutrient iodine, one of the important environmental regulator of thyroid gland functions that regulate not only growth, development and maintenance of body functions at the different stages of life of humans and animals but intimately related with the socioeconomic development of a country. Iodine deficiency is the world’s greatest single cause of preventable brain damage and mental retardation manifesting itself as goiter and a range of physical and mental handicap, collectively included the term Iodine Deficiency Disorders (IDD). Environmental iodine deficiency of the earth is forever a reality, and iodine deficiency in the population is forever a risk. Thus there is a need to establish more comprehensive multi-country surveillance of iodine nutrition. IDD are considered as a public health problem and iodine supplementation though the primary regulator but it is not the only way of its prevention and control in India as experienced by the work. In the topic ‘Thyroid Functions in Iodine Deficiency and *Department of Physiology, University of Calcutta, 92, A.P.C. Road, Kolkata 700 009, India, Email: [email protected] 4 Proc. 98th Indian Science Congress Part II : Presidential Address Region Specific Environmental Goitrogens - their impact in life and society’ almost all the aspects of this public health problem will be highlighted. Introduction In 1811, France was at war, and Bernard Courtois was producing saltpeter for gunpowder for Napoleon’s army. He was burning seaweed to isolate sodium bicarbonate and he added sulfuric acid to the ash which produced an intense violet vapor that crystallized on cold surface. He sent the crystal to Gay-Lussac, who identified it as a new element, and name it to iodine, from the Greek for “Violet”. The ancient Greeks used the marine sponge to treat swollen gland because the sponge and dried seaweed remained a ‘goiter cure’ since Middle Ages. In 1813, learning of the discovery of iodine in seaweed, Coinder, a physician in Geneva, hypothesized the traditional treatment of goiter with seaweed or sponge was effective because of its iodine content. He began giving oral iodine tincture to goitrous patients at an initial daily dose of 165mg. This provoked strong opposition among the medical profession. Although Coinder insisted his treatment was safe, however the debate on the safety of iodine continued till the early 20th century. The French chemist Boussingault was the first who advocated iodine-rich salt as a prophylaxis in the prevention of goiter. It will be nearly 100 years before their vision was realized. Another French chemist Chatin in 1851 for the first time published the hypothesis that iodine deficiency is the cause of goiter. However Chatin’s work was greeted with great skepticism by the French Academy of Science. Despite this, French authorities began distributing iodine tablets and salt together with prophylactic measures where goiter was severe. The program was clearly effective: in a survey of 5000 goitrous children, 80% were cured or improved by the iodine treatment. The doses of iodine administrated both in table salt and tablets were too high. The high dose of iodine was consistent with the enormous doses of iodine used to treat many diseases as scrofula, syphilis, arthritis. Many people tolerated the high doses of iodine well but it caused iodine-induced hyperthyroidism in some individuals, and as a result, the program was discredited and discontinued. Cretinism occurred only in endemic goiter affected areas was recognized by Medical authorities but they were puzzled by the fact that many cretins had an atrophic or absent thyroid gland i.e. the opposite of goiter. A clue of this problem appeared when a related disease, myxedema, that resembled cretinism, was described in 1977 by Ord in London. In Section XI: Medical Sciences (Including Physiology) 5 1983, Seman suggested myxedema was for the lack of activity of the thyroid after reading a report of the of Swiss surgeon Theodor Kocher (1841-1917) Nobel Lauret in 1909, who described myxedemic symptoms in patients after total thyroidectomy. British physicians began successfully treating myxedema with injection, and/or oral doses of animal thyroid extracts. In 1886, Baumann and Ross found link between goiter, myxedema and iodine while working in Freiburg, Germany. While they were digesting animal thyroid glands, were surprised to isolate residual fraction that was iodine. They termed this substance ‘thyroiodine’ not only therapeutically active in the treatment of myxedema and goiter, but a constituent of organic molecule. Since then many prophylaxis studies inducted to evaluate the impact of iodized salt of which a few are cited below Impact of iodized salt in Switzerland The Swiss physician, Beyard in 1918 did the first dose-response trial of iodine to treat goiter. He did this in Grachen, an isolated village at the base of Matterhorn in the Zermatt valley. He gave iodized salt for 6 months to families in the village with their different iodine contents (3, 6 and 15 mg/kg). Bayard showed that as little as 30µg of iodine daily had beneficial effect on goiter and noted soft diffuse goiters in children were more responsive than nodular forms. Accordingly in 1922, the Swiss Goiter Committee cautiously advised the introduction of salt at 1.9 to 3.75 mg/kg nationwide as a voluntary basis, a compromise between proponents and opponents of iodized salt. The first canton in which iodized salt was introduced was Appenzell AR in 1922, where the salt was iodized at 7.5 mg/kg with spectacular results: newborn goiter disappeared, no new cretins were born and goiters in children were reduced in size or disappeared. Iodine prophylaxis in Akron, Ohio, USA Almost at the same time, during 1915-1919, Marine and Kimball introduced iodine prophylaxis in the Midwest region of U.S. Baumann’s observation that large goiters contained less total iodine than in healthy glands was further confirmed by Marine. Marine suggested that goiter was “a compensatory reaction to some deficiency” and it appeared “iodine is the most important single factor”. Marine realized goiter was a serious public health problem and in 1916 he planned to intervene within iodine in school-children in Cleveland. But his plan was refused considering iodine was a poison. With the help of Kimball, Marine conducted the study in neighboring Akran, Ohio. The treatment group of girls received 6 Proc. 98th Indian Science Congress Part II : Presidential Address 200-400 mg NaI/school day for 10 days. The treatment was effective and they concluded that goiter was preventable in man as well as in fish or in domestic animals. Based on these studies, general prophylaxis with iodized salt was introduced in the state of Michigan in 1924. There was great protest however in 1948, the U.S. Endemic Goiter Committee tried to introduce iodized salt to all the sates by federal law but failed (Zimmermann, 2009). Effectiveness of iodine prophylaxis in Kangra Valley, India In order to substantiate the role of iodine deficiency as the causative factor for the endemic goiter in the Himalayan belt and to the study the effectiveness of iodine prophylaxis, a prospective study was organized in 1956 in a population of approximately 1 lak persons in Kangra Valley of Himachal Pradesh in India. Table 1. Effect of iodized salt on the prevalence of goiter in school children of the Kangra Valley, India Zone Sex Prevalence of goiter (%) 1956 1962 1968 A Male 34.1(2019) 19.3(2539) 7.5(1683) Female 51.4(510) 18.4(956) 10.4(822) B Male 34.2(1605) 39.8(3262) 17.2(1507) Female 51.7(422) 41.5(1282) 17.0(1032) C Male 36.0(2338) 14.5(2527) 8.4(1821) Female 47.4(626) 14.9(893) 10.6(856) Source : From Sooch et.al (1973). Notes: The Kangra Valley is in the Himalayan foothills. The study region was divided into A, B, and C zones. After a baseline survey in 1956, the salt distributed to zones A and C was fortified with potassium iodide and potassium iodate, respectively while zone B was supplied with unfortified salt. The salt fortification was at a level that supplied approximately 200ug of iodine per person per day. After 6 years of iodization, in 1962, a marked decrease in the prevalence of goiter was observed in zone A (from 38% to 19%) and zone C (from 38% to 15%) without any significant change in zone B. Six years later, in 1968, a systemic survey of goiter prevalence showed a further reduction in zones A and zone C (8.5% and 9.1%, respectively).

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