Thyroid for Dummies (25 page)

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Realising the Vastness of the Problem

More than one-quarter of the world’s population suffers from some level of iodine deficiency disease. That portion works out at 1.6 billion people. Of these people, 655 million have a goitre, 26 million have brain damage, and 6

million of those 26 million are classed as ‘cretins’ – a somewhat unfortunate term, which means that the individuals are so handicapped due to their thyroid condition that they’re completely dependent upon those around them to live. Some researchers estimate that for each day we delay treating this vast problem, 50,000 more infants are born with decreased mental capacity due entirely to iodine deficiency.

The reason so many people suffer with this condition is that the food they eat contains little or no iodine, mostly because the ground on which it’s farmed is depleted of iodine. Chapter 3 explains that iodine is required to form thyroxine (T4) and triiodothyronine (T3), the two major thyroid hormones – in fact, this requirement is the only known function of iodine in the body.

All the earth’s soil used to contain iodine. However, hundreds of thousands of years have seen iodine leached out of the soil in two major areas of the earth: The high mountains and the plains that were covered with fresh water in the past, which were far away from oceans. The high mountains were once covered with glaciers. As the glaciers melted, they carried iodine out of the soil, back to the ocean. In the same way, the flooded plains leached iodine from the soil and carried it back to the ocean as the water flowed away. As a result, high mountains and plains far from oceans are the areas where iodine deficiency disease is most often found.

Crops that grow in such soil are iodine deficient, as are the animals that feed on these crops. If the animal is a cow that provides milk, children who drink that milk are at risk of iodine deficiency. The meat from that cow is also iodine deficient. The result is a huge public health problem. Even pets such as dogs become iodine deficient.

If you look at a map of the world that shows the areas where iodine deficiency disease is most prevalent, you see that vast areas of China, Russia, Mexico, South America, and Africa are rife with the disease. Surprisingly, even developed countries such as the United Kingdom are not spared. In fact, Derbyshire Neck was at one time the common name for a goitre, as iodine deficiency was so common in this part of England. The iodisation of salt and cattle feed helped to solve the problem, but with the current health advice to cut back on salt intake, concern is growing that the problem may recur. In the United States, for example, nearly 12 per cent of people in one study showed evidence of low iodine levels, compared with only 3 per cent 20 years earlier.

Recent studies among Europeans show decreases in iodine intake as well.

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How iodine deficiency is measured

To determine whether iodine deficiency is pre-

The second important measure of iodine defi-

sent in large populations, the development of

ciency is the frequency of goitres. Traditionally,

simple tools to measure a lack of iodine is nec-

a goitre is diagnosed if the lobes of the thyroid

essary. One technique is to measure the amount

are larger than the end parts of the thumbs of the

of iodine excreted in urine. In areas where

person concerned. (These parts are called the

iodine is not deficient, the iodine in the urine is

terminal phalanges of the thumbs.) Unfortunately,

100 micrograms per day or more.

such a measurement of the thyroid is hard to

make in practise, especially for small children in

If a country or population undertakes an iodisa-

whom it’s most important. To overcome this diffi-

tion programme, this urine test is carried out on

culty, doctors use a portable ultrasound device

a sample of the population before they receive

(refer to Chapter 4), which produces a measure-

iodine, and again at intervals afterwards to see

ment that is highly accurate and reproducible.

whether the programme is working. (If it is, a

much higher level of iodine appears in the urine

Finally, measurement of thyroid hormones and

after iodisation begins.)

TSH in the blood helps to evaluate the produc-

tion of thyroid hormones.

Facing the Consequences of Iodine Lack

If your body lacks iodine, it can’t produce sufficient thyroid hormone. This deficiency has severe consequences at every stage of life. This section discusses the price paid in poor health and abnormal function at every stage of life, beginning with a pregnant woman and her baby.

Pregnancy

Even before pregnancy, a lack of T4 hormone appears to affect fertility.

Women who are hypothyroid have greater difficulties becoming pregnant, and they have more miscarriages and stillbirths than women with normal thyroid function.

A foetus (developing baby) doesn’t begin to make thyroid hormone until the 24th week of pregnancy. Until then, it’s dependent upon the mother’s T4.

During this time, the foetal brain is developing, and the entire chain of events that produces a normal brain requires T4 at every stage. If this hormone is lacking, the consequences are severe.

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If a foetus is deficient in T4, this need triggers an increase in the amount of the enzyme that converts T4 to T3 within the brain. This form of the enzyme is not found in other tissues, so the brain is partially protected from hypothyroidism while the rest of the body is not.

The entire body’s formation is dependent upon adequate T4. If sufficient hormone is not available, congenital anomalies may occur and the infant may not survive much past birth. If it does, the infant may not live more than a few years. In this nuclear age, it’s important to realise that a thyroid gland that is not making enough thyroid hormone will take up large amounts of iodine from whatever source it can. In the case of a nuclear accident, where radioactive iodine is released, a hypothyroid mother will concentrate the iodine and pass it on to her growing foetus. If radioactive iodine does not completely destroy the developing foetal thyroid, that thyroid is very prone to develop thyroid cancer in the future.

Infancy

A new baby deprived of iodine has a goitre and shows signs of hypothyroidism. Depending upon the severity of the lack, the baby may have cretinism, which this chapter explains later on. The brain of a newborn continues to develop up to the age of two years, so giving adequate amounts of iodine immediately after birth may help to prevent problems with mental development. A baby lacking in iodine also shows increased susceptibility to radioactive iodine (or any iodine) and is therefore more vulnerable if exposed to increased levels as a result of a nuclear accident such as occurred in Chernobyl.

Childhood

Iodine-deficient children often have goitres. Their intelligence is usually affected, their motor function (muscle control) is poor and they are sometimes deaf. Like infants, these children have a tendency to accumulate iodine from any source and are at greater risk in the case of a nuclear accident.

Adulthood

After an iodine-deficient child grows up, he often has a goitre if they develop into an iodine-deficient adult, though not always. He usually has special intellectual needs, and may have movement difficulties. This person’s thyroid gland is highly susceptible to radioactivity.

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The costs of iodine deficiency disorder are enormous both for the individual and for society.

Endemic Cretinism

Shabmir is a 46-year-old woman living in Pakistan. She has a huge growth on the front of her neck that the doctors tell her is a goitre. She isn’t alone, because more than 70 per cent of the villagers around her suffer from the same condition.

Shabmir has little aptitude for learning and, because of the unsightly growth on her neck, she is discriminated against by those who do not have the same problem (perhaps because they come from an area with sufficient iodine in the food). Not only that, the goitre is so large that she has difficulty moving her head and neck, which makes earning a living difficult. Her husband also has a severe goitre, which is the only reason he agreed to marry her.

Shabmir is unable to have a baby. The one time she finds she is pregnant, the baby is stillborn. She does not manage to get pregnant again.

She appears swollen and lethargic. She has little interest in her neighbours or her surroundings, and she tends to sleep a lot.

Shabmir’s story is typical of the way that iodine deficiency disease affects the lives of millions of people. Whole populations are rendered unable to function by this worldwide plague. A village of people with iodine deficiency disease is unable to govern itself or provide an economic base to help better the condition of the people, or to take the steps necessary to overcome the problem, including using iodine. The shame is that this condition is completely preventable.

This section describes the different ways that iodine deficiency disease appears in people. The manifestations of iodine deficiency disease are far worse than the hypothyroidism commonly found in the United Kingdom (refer to Chapter 5) because the hypothyroidism associated with lack of iodine begins when babies are conceived. Their mothers are already hypothyroid.

Unless and until the chain of iodine deficiency is broken with the provision of sufficient iodine, the disease continues to disrupt the lives of a quarter of the world’s population.

Endemic cretinism
is the term used for the group of signs and symptoms that are found when severe iodine deficiency affects a significant proportion of a population. Endemic cretinism consists of several features:

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ߜ More than 5 per cent of children age 6 to 12 have enlarged thyroid glands associated with endemic goitre.

ߜ Those affected have problems with mental function and show either

• Predominantly nervous system symptoms (such as defects of hearing and speech) as well as problems with standing and walking, which is called
nervous cretinism
, or

• Symptoms of hypothyroidism and reduced growth called
myxoedematous cretinism

ߜ In areas where iodine is adequately replaced, cretinism does not occur.

Figure 12-1 shows a typical goitre on a person living in an area of endemic cretinism.

Figure 12-1:

A typical

goitre on a

person

living in an

area of

endemic

cretinism.

Looking at the geographic distribution

Endemic cretinism is found in the mountain regions of the world, as explained earlier in this chapter. The condition is most commonly found in the Andes and the Himalayas. It occurred in the Alps until iodine replacement 18_031727 ch12.qxp 9/6/06 10:43 PM Page 139

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began several decades ago, but areas do still exist there where people don’t get sufficient iodine. Endemic cretinism is found in mountainous regions of China, the Pacific, and the Middle East, and in lowlands away from the ocean where heavy rains wash iodine out of the soil. The condition is also present in central Africa, in central Brazil, and even in Holland.

In Europe, iodine deficiency disease remains a significant problem in numerous countries, including: Austria, Belgium, Bulgaria, Russia and some of the former Soviet States, Croatia, Germany, Greece, Holland, Hungary, Ireland, Portugal, Romania, Spain, and Turkey.

Australia has the problem of endemic cretinism in its mountainous regions, especially Tasmania.

In South Asia, iodine deficiency disease is common in Bangladesh, India, Nepal, Tibet, and Pakistan.

In Southeast Asia, large populations of people with goitres are found in Burma, Vietnam, Thailand, and New Guinea.

In Central and South America, large populations lack iodine in Bolivia, Brazil, Chile, Ecuador, Mexico, Peru, and Venezuela – mostly in the Andes Mountains and the mountains of Mexico.

In Africa, endemic cretinism is found in Cameroon, the Central African Republic, Nigeria, Uganda, Rwanda, the Sudan, Tanzania, Zaire, and Zimbabwe.

Contributing factors

Lack of iodine is, without a doubt, the main factor in endemic cretinism, but other issues definitely play a role in different areas of the world. Dietary factors other than iodine consumption are a major aspect of iodine deficiency disease.

In some areas of iodine deficiency disease, the normal diet includes substances that are harmful to the thyroid. In Africa, for example, cassava is a major part of the diet – cassava is a starchy tuberous tree root often used in cooking in the form of flour. Cassava contains cyanide, which is destroyed only if the food is properly prepared. If not, the cyanide is converted into thiocyanate in the body. Thiocyanate competes with iodine for uptake in the thyroid; thus, decreasing even further the tiny amount of iodine that gets into the thyroid. (If someone consumes sufficient iodine, it overcomes any block from thiocyanate.)