INTRODUCTION:

Iodine is a micronutrient of crucial importance for the health and wellbeing of all individuals. It is a trace element, just 5 gm of which are sufficient to meet the life time needs of an individual with a lifespan of 70 years¹. Iodine is mostly concentrated in thyroid gland². A healthy adult body contains 1520mg of iodine, 70-80% of which is stored in the thyroid gland. Daily intake of iodine by an individual amounts to 500 micrograms; Daily physiological requirement during adult life is 150 micrograms; During pregnancy and lactation period is 200 micrograms; and during neonatal period is 40 micrograms³.

Normally about 120 micrograms of iodide are taken up by the thyroid gland for the synthesis of thyroid hormones⁴.

Role of iodine in thyroid physiology:

Iodine is a trace element in soil and water that is ingested in several chemical forms. Most forms of iodine are reduced to iodide in the gut⁵. Iodide is nearly completely absorbed in the stomach and duodenum⁶. Iodine is cleared from the circulation primarily by the thyroid and kidney. Under normal circumstances, plasma iodine has a half-life of approximately 10 hours, but this is shortened if the thyroid is overactive, as in iodine deficiency or hyperthyroidism. The mean daily turnover of iodine by the thyroid is approximately 60–95 μg in adults in iodine-sufficient areas. The body of a healthy adult contains from 15 to 20 mg of iodine, 70%–80% of which is in the thyroid. In the basolateral membrane of the thyroid cell, the sodium/iodine symporter (NIS) transfers iodide into the thyroid across a concentration gradient 20–50 times that of plasma by active transport⁷.

Degradation of T4 and T3 in the periphery releases iodine that re-enters the plasma iodine pool⁸. Most ingested iodine is eventually excreted in the urine. Only a small amount appears in the feces.

Control of the thyroid by iodine:

Iodide is known to control thyroid function. Its main effects are to decrease the response of the thyroid to thyrotropin (TSH); to acutely inhibit its own oxidation; to reduce its trapping after a delay; and, at high concentrations, to inhibit thyroid hormone secretion. Small changes in iodine intake are sufficient to reset the thyroid system at different serum TSH levels. This suggests that modulation of the thyroid response to TSH by iodide plays a major role in the negative feedback loop⁹. In response to increasing doses of iodide, iodine organification increases initially and then decreases. This acute inhibition of organification, termed ‘the Wolff-Chaikoff effect’, results from a high concentration of inorganic iodide within thyroid cells^10-11.The mechanism responsible for inhibition of organification is unclear, but it may be caused by inhibitory effect of iodide on thyroid peroxidase or some other enzymes¹². In normal subjects who have been given iodide, the inhibition of organification is transient and this phenomenon is termed ‘escape from the Wolff-Chaikoff effect’ or ‘adaptation to the Wolff-Chaikoffeffect’¹³.

Iodine deficiency disorders:

Iodine is mostly obtained from food sources particularly vegetables grown on iodine richsoil; The remaining requirement is met from drinking water¹. Seaweeds such as wakame, nori or mekabu, which are widely used in some Asian cultures for making soups, salads and condiments, are rich sources of iodine. Iodine is found in nature in various forms: inorganic sodium and potassium salts (iodides and iodates); Inorganic diatomic iodine (molecular iodine or I), and organic monoatomic iodine ¹⁴.

Oceans are the world's main repositories of iodine and very little of earths iodine is actually found in the soil. The deposition of iodine in the soil occurs due to volatilization from ocean water, a process aided by ultraviolet radiation. The coastal regions of the world are much richer in iodine content than the soils further inland; Here the problem gets more compounded by continuous leeching of iodine from the soil¹⁴. Therefore, the crops grown in such soil remain iodine deficient; Even ground water in these areas is deficient in iodine². This explains the endemic distribution of Iodine Deficiency Disorders (IDD) in the world.

Worldwide, Iodine Deficiency Disorder (IDD) remains a significant public health problem in 130 countries, although it has been eliminated in 61 countries (UNICEF /WHO, 2001). It is estimated that approximately 740 million people (13% of total population) are affected by goiter while 2,225 million people (38%) are at risk of IDD. Eastern Mediterranean (32% of its population), Africa (20%), Europe (15%) and Southeast Asia (12%) have high prevalence of goiter. In Asia, IDD is widespread with prevalence of to talgoiter rate (TGR) among school children ranging from 4% to50%. IDD is particularly severe in India near the Himalayas¹⁵.

There are several manifestations of iodine deficiency now termed iodine deficiency disorders. Majority of these disorder manifests in infants and children mainly due to maternal iodine deficiency. Hearing loss, learning deficits, brain damage, and myelination disorders can occur due to fatalor perinatal hypothyroidism. Infant mortality rates have decreased 65 percent in communities where iodine deficiencies have been eliminated. Maternal iodine deficiency manifests as low thyroxin, elevated thyroid stimulating hormone (TSH), and subclinical thyroid enlargement (subclinical goiter). As pregnancy and lactation increase iodine loss, the risk for goiter continues, and even after lactation ceases it may manifest as multinodular goiter and hyperthyroidism¹⁶.

Iodine deficiency in women can lead to over hypothyroidism and consequent an ovulation, infertility, gestational hypertension, spontaneous first-trimester abortion. The importance of iodine as an essential micro-nutrient arises from the fact that it is a constituent of the Thyroidhormone, Thyroxin T4 and Tri-iodo Thyroxin T3 essential for normal physical and mental development in humans and animals and also for the development of the brain and maintenance of body temperature. A deficiency of thyroid hormone from any cause will lead to severe retardation of growth and maturation of almost all organ systems. Healthy adult human body contains 10 to 20 mg of iodine of which 70% to 80% is found in the Thyroid gland¹⁷. Iodine is rapidly absorbed through the gut. The normal intake and requirement per person is 100-150 μg/day. Excess iodine is excreted through the kidney, which correlates well with the level of intake. About 90% of iodine is excreted in urine¹⁸.

The tribal population is considered to be one of the most disadvantaged groups in accessing the health care services and various other health policies. The adoption of family planning methods is way behind in this group and the finding of the study of 55.34% women as multipara reflects the same. 20.08% of the women in the study had the history of abortion & still birth. Abortion and still birth is one of the most dreadful results due to subnormal intake of iodine during the reproductive age ¹⁹.

Since iodine is released from the body through urine, the best way to determine iodine deficiency across a large population is to measure the amounts of iodine in urine samples. The WHO defines iodine deficiency as a median urinary iodine concentration less than 50 μg/L in apopulation²⁰.

With increasing awareness of the wide spectrum of iodine deficiency disorders, a steady increase has been noticed in the estimation of the magnitude of the problem in the world. In 1990, WHO reported that the total population at risk of iodine deficiency in developing countries was 1 billion, of which 200 million suffered from goiter; Over 5 million were cretins with gross mental retardation; And 15 million had less degrees of mental defect. In India, 150 million people are estimated to be exposed to the risk of iodine deficiency disorders of which 54 million have goiter, 2.2 million are cretins and 6.6 million have neurological defects ²¹. Still births and neonatal deaths attributable to iodine deficiency exceed 90,000. The world's most intense endemic belt lies in India which runs along the southern slopes of Himalayas, extending from Kashmir in the west to the Naga Hills in the east. With increasing awareness of the problem, “extra-Himalayan” foci of iodine deficiency have been discovered in the country ¹. As of today, not a single state in India can be absolved of the iodine deficiency problem.

The bioavaibility of iodine applied to the skin:

The best study of the bioavailability of iodine applied to the skin in normal human subjects was reported by Miller, et al, in1989²².The purpose of Miller’s study was to assess the effectiveness of skin application of iodine in blocking radio iodide uptake by the thyroid gland. The subjects used in this study were 24 adult malevolunteers aged from 21 to 51 years.

These subjects were divided into four groups of six subjects each. One group served as control and did not receive stable iodine. The other subjects in the remaining three groups received respectively 130 mg KI orally equivalent to approximately 100 mg iodide; 80 mg iodine (tincture) on the skin; and 160 mg iodine on the skin. All 24 subjects ingested 131I labeled NaI and radioiodide thyroid uptake was measured at 2 hours, 6 hours, and 24 hours post-ingestion of radioactive iodide. Serum inorganic iodide levels were measured at time zero, 2 hours, 6 hours and 24 hours postintervention. Twenty-four-hour radioiodide uptake by the thyroid gland as percent of dose administered was used to assess the effectiveness of iodine in blocking radioiodide uptake by the thyroid. The 24-hourpercent radioiodide uptake by the thyroid gland were:

· Control: 10.9±2.9% (SD)

· Oral KI: 0.34±0.26%

· Skin 80 mg iodine: 7.0±5.5%

· Skin 160 mg iodine: 2.0±2.5%

Prior to administration of stable iodine, the mean serum iodide in the three intervention groups were0.024 mg/L, 0.033 mg/L, and 0.02 mg/L. The mean of the three mean values is 0.026 mg/L. Under steady state conditions, the computed daily intake of iodine based on serum iodide is equal to the product of serum iodide times 43.5 L/day, which is the renal clearance of iodide.3 The estimated average daily intake of iodine by this group of men is 0.026 mg/L × 43.5 L/day = 1.13 mg/day. This daily intake may be due to the iodization of bread in the 1960s and 1970s and in some states in the 1980s. The estimated daily intake of iodine during that time in the US was 1 mg. This computed daily intake in Miller’s subjects is in agreement with the mean percent radioiodide uptake by the thyroid gland in this group of subjects with a mean of 10.9.

Life saving dot:

What’s the best way to drive home a message or get people to adopt a practice? One way is to integrate it with something that is a part of their life, or create an incentive for them to do so. There have been quite a few campaigns that have managed to do that and the latest among these is the Jeevan Bindi or Life Saving Dot, launched as a pilot project in Maharashtra and Delhi.

The Nashik based Neelvasant Medical Foundation & Research Center wanted to find a way to address the iodine deficiency among women. Millions of women across rural India are affected by breast cancer, fibrocystic breast disease and complications during pregnancy. Studies reveal that many of these cases are linked to iodine deficiency. There are supplements and treatments to address this but they are unaffordable to these women. In stepped Grey for Good, advertising group Grey Singapore’s philanthropic arm, and Talwar Bindi to collaborate with the foundation to develop iodine patches that would serve as bind is to deliver the women their daily dose of iodine²³.

Figure 01: Iodine patches entitled as Life saving dot

Since mid-March, the bind is have been distributed to Badli village (near New Delhi), Niphad, Peth and Kopergaon/Sinner rural and tribal districts of Maharashtra. India’s salt iodisation mission dates back to the late 1950s when a study in the Kangra valley established iodine deficiency as the cause of goitre and recommended that adding it to salt was the most economic and viable means of preventing it. In the ’80s, private manufacturers too were allowed to iodise salt and it also found a place in the public distribution system in many States²³.

Figure 02: A woman representing Iodine patch as a Bindi

However, it is still an elusive commodity for many sections of the poor. Dr Prachi Pawar, President, Neelvasant Foundation, tells catalyst that the families in the project’s area used uniodised crystal salt. The daily recommended dose of iodine is 150-200mcg. Around 80-90per cent of Indian women wear bind is. Using them as devices to deliver iodine through the skin was seen as a simple and effective way to get around the problem. Subdermal delivery and absorption of iodine is a tried and tested technique, she says. The iodine is mixed with the adhesive on the bindis. The women are given a month’s supply. The project is expected to scale up in the second phase. Manufacture of the bindis by the women as a revenue generation strategy is also on the radar, says Dr Pawar²³.

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23. A dOt with a mission, 07^th August, 2017 http://www.the hindubusinessline.com/catalyst/a-dot-with-a-mission/article7085099.ece

Received on 12.08.2017 Accepted on 28.10.2017

Asian J. Pharm. Res. 2017; 7(4): 225-229.

DOI: 10.5958/2231-5691.2017.00035.1