Thyroid for Dummies (42 page)

Sometimes, the surgeon can leave enough thyroid tissue to retain thyroid function while eliminating hyperthyroidism, but the child is checked at least every six months to a year to detect recurrence or loss of thyroid function and the need for thyroid medication.

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Diagnosing Goitres in Children

An enlarged thyroid gland is actually the most common thyroid abnormality found in children. It occurs in about 5 per cent of all children. A child with an enlarged thyroid usually has normal thyroid function.

The most common cause of thyroid enlargement in children is autoimmune thyroiditis (refer to Chapter 5). The second most common cause is a multinodular goitre (refer to Chapter 9).

Telling these causes apart is important because autoimmune thyroiditis can lead to hypothyroidism (or sometimes hyperthyroidism), whereas multinodular goitre does not. Obtaining thyroid autoantibody studies can tell the difference, pointing to autoimmune thyroiditis if the results are positive.

Testing the child’s levels of free T4 and TSH verifies whether his or her thyroid function is normal.

These goitres sometimes get smaller and then larger again, sometimes growing at different rates in different parts of the thyroid, leading to a multinodular thyroid gland.

Treatment is given if the large thyroid is pressing on nearby structures like the oesophagus and trachea, or is disfiguring. The treatment is either surgery or radioactive iodine. The thyroid is checked every six months for a few visits, then yearly.

If the goitre is painful, the diagnosis is more likely subacute or acute thyroiditis (refer to Chapter 11). These diseases cause similar signs and symptoms in children as they cause in adults. Subacute thyroiditis generally makes a child less sick than acute thyroiditis. Subacute thyroiditis affects the whole gland, whereas acute thyroiditis may swell only part of the gland. If acute thyroiditis occurs several times, this occurrence can be due to a malformation in the thyroid that requires surgery to correct it.

Linking Nodules and Cancer in Children

Children rarely get thyroid nodules, but when they do, the nodules indicate cancer more frequently than they do in adults. The signs that make a nodule particularly suspicious for cancer are the same as in adults: ߜ Rapid growth

ߜ Painlessness

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ߜ Firmness and fixation

ߜ Nodes felt in the neck

While a functioning nodule or a cystic nodule (refer to Chapter 7) is rarely cancerous in an adult, this case isn’t true in children.

A very important clue that a child’s nodule is cancerous is past exposure to irradiation. Exposure leads to nodules and cancer in multiple places in the thyroid. (The leading type of thyroid cancer in both children and adults is papillary – the type of cancer most closely associated with irradiation exposure.)

A fine needle biopsy of the nodule is carried out if the doctor suspects cancer, but this test isn’t as helpful in children as it is in adults. A 1996 study in the
Journal of Pediatric Surgery
shows that a correct diagnosis of thyroid cancer is made in only 3 of 7 biopsies. It’s not clear why this result is so –

perhaps because a child’s nodule is small and easily missed by the needle.

Children tend to have more cancer spread into the neck and into the lungs at the time they are diagnosed than adults, but this fact does not make their prognosis worse. The cancer is managed just like adult cancer with a total thyroidectomy (refer to Chapter 13), preserving the parathyroid glands and the recurrent laryngeal nerves. This surgery is followed with radioactive destruction of the remaining thyroid tissue. The patient is placed on thyroid hormone to replace the thyroid and to suppress growth of new thyroid tissue.

Children with thyroid cancer are monitored with thyroglobulin blood tests; this test should read close to 0 shortly after surgery. The blood tests are carried out every six months to a year. If the level of thyroglobulin rises, a whole body scan is needed to look for any tissue that takes up iodine. The scan may use new recombinant TSH (refer to Chapter 14) so the patient does not have to stop taking thyroid hormone to perform this study. If all the iodine is found in the neck, local surgery is often enough to eliminate the additional thyroid cancer tissue. If the tissue is spread around the body, a large dose of radioactive iodine destroys it.

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Chapter 20

Maturing: Thyroid Disease

in Later Life

In This Chapter

ᮣ Discovering how many older people have thyroid disease

ᮣ Recognising the difficulty of diagnosis

ᮣ Dealing with hypo- and hyperthyroidism

ᮣ Treating thyroid nodules in older people

Before talking thyroids, you need to know that ‘older people’ are those aged 65 or older. Not that far away! And most people over that age still feel young thanks to the knock-on effects of the fact that 50 is undoubtedly the new 40. Compared with just a few generations ago, modern people in later life are usually more outgoing, active, and generally more youthful.

Even so, older people are often afflicted with thyroid disease – a diagnosis that’s often missed for two key reasons. First, when an older person goes to a doctor, hospital, or nursing home, the illness or condition that prompts him or her to seek care is, naturally, the doctor’s primary focus. Secondly, symptoms of thyroid disease often mirror symptoms of other conditions so, even if the doctor looks for these other conditions, thyroid disease itself is often overlooked.

When doctors are taught about disease, they learn a set of signs and symptoms that are characteristic of each particular illness. Unfortunately, older people with thyroid disease may have no typical symptoms, and when they do occur, their symptoms are often the opposite of those expected. The only way doctors are going to discover thyroid disease in many older people is with screening – obtaining thyroid function tests from a person who appears healthy – but this step is controversial.

Screening for thyroid disease in older people has its own problems, as screening picks up a lot of subclinical disease – a situation where one blood test is not normal but another is, and the patient is otherwise well. There’s 27_031727 ch20.qxp 9/6/06 10:45 PM Page 248

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tremendous controversy concerning what to do with subclinical thyroid disease. As a community, doctors haven’t yet made any final decisions about whether to treat subclinical thyroid disease, wait for symptoms to develop, or wait for both thyroid blood tests to become abnormal.

Assessing the Extent of the Problem

To determine how many older people have thyroid disease, doctors need to decide what ‘thyroid disease’ actually means. Is having an abnormal TSH

level sufficient to make a diagnosis, or is an abnormal free T4 level needed as well? (Check out Chapter 4 for information about these tests.) This question is difficult to answer in older people because they often have so many symptoms, many of which relate to other conditions. Some doctors consider an abnormal TSH is insufficient evidence of thyroid disease, and use the term
subclinical
to describe the situation where the TSH is abnormal but the free T4 is normal. Some doctors do not support treating a patient with subclinical thyroid disease. Yet many studies show that treatment reduces or eliminates many of the symptoms. On the other hand, treating an older person, particularly with thyroid hormone for hypothyroidism, is not always helpful, as this chapter discusses later.

In one study from the United Kingdom, published in the
Archives of Internal
Medicine
in January 2001, all patients age 65 or older were tested for thyroid disease when entering hospital. Out of 280 patients (leaving out those with known thyroid disease), 9 had hypothyroidism and 5 had hyperthyroidism that was not previously suspected. An additional 21 people had subclinical hypothyroidism (high TSH, normal free T4), and 12 had subclinical hyperthyroidism (low TSH, normal free T4). Overall, nearly 40 per cent of the older people not thought to have thyroid disease had some evidence of it. Do all these people need treatment?

Writing in rebuttal to this study, other authors suggest that many older people with subclinical disease actually have temporary abnormalities due to other conditions.

In another study of older people not in hospital, unsuspected hyperthyroidism was discovered in 1 per cent, and unsuspected hypothyroidism was discovered in 2 per cent. So, 3 of 100 older people are walking around with clinical thyroid disease. This figure may not seem like a lot, but in the population of the United Kingdom, where 16 per cent of the population are aged 65 and over, this fact means that more than 290,000 older people are walking around with undetected and highly treatable thyroid disease. (That number does not even account for the age group 35 to 65, which contains many more cases of undiagnosed thyroid disease.)

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Large population studies have shown that 10 per cent of women over age 65

have elevated TSH levels. Most of them do not have symptoms of thyroid disease. Isn’t it interesting that there’s no argument about screening babies for thyroid disease (when the occurrence of abnormal tests is 1 in 3,750), yet the debate continues about screening older people (when 3 in 100 cases of clinical thyroid disease are likely)?

Some doctors believe that everyone should have screening for thyroid disease beginning at age 35 and every five years thereafter. Unfortunately, costs get in the way, even though screening is easily done with a TSH test. If this test is abnormal, then a free T4 test is done. If both tests are abnormal, the patient is treated for thyroid disease. If only the TSH is abnormal, it’s reasonable to take a careful history and do a physical examination, and then decide on treatment based upon that evaluation.

Understanding Sources of

Confusion in Diagnosis

The natural consequences of ageing, the many complicating diseases found in older people, and the effects of medication can all confuse a diagnosis of thyroid disease. In fact, ageing and other diseases can cause symptoms that are identical to those found in thyroid disease. Medications can also affect laboratory tests to confuse the diagnosis even further (refer to Chapter 10).

Diagnosing thyroid problems in older people therefore requires the detective work of a medical Sherlock Holmes.

Acknowledging other diseases

Certain diseases that affect thyroid test results are found more often in older than in younger people making the outcome appear as if a person has thyroid disease when they do not. The most common confusing factors in thyroid testing are

ߜ Poor nutrition

ߜ Poorly controlled diabetes

ߜ Liver disease

ߜ Heart failure

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Any severe illness can also cause a temporary fall in T4 that is sometimes misdiagnosed as hypothyroidism.

Taking medications

Drugs often taken in later life that can alter thyroid function tests include the following:

ߜ Epilepsy drugs, such as carbamazepine and phenytoin, cause the rapid breakdown of thyroid hormones in the liver which, in turn, lowers thyroid hormone levels in the blood.

ߜ Aspirin decreases the binding of thyroid hormones to thyroid-binding globulin, which lowers the total (but not the free) T4.

ߜ Corticosteroid drugs, such as prednisone, decrease thyroxine-binding globulin levels.

ߜ Drugs for abnormal heart rhythm, particularly amiodarone, can cause both hypothyroidism and hyperthyroidism.

ߜ Heparin, used for anticoagulation, can cause a temporary rise in T4 as it displaces it from binding proteins.

Discovering Hypothyroidism

in Older People

Victor is a 68-year-old man who is feeling a bit fatigued. He has put on a few pounds, and feels cold when others seem comfortable. He also notices that he is more constipated than before. Victor thinks all these changes are the natural effects of ageing. Although he doesn’t like to talk about it, his constipation is now a serious problem, and this symptom is what brings him to his doctor. The doctor observes that Victor’s pulse is slow and that his eyebrows and eyelashes are rather sparse. He tells Victor that he believes this fact is due to hypothyroidism and sends him for thyroid function tests.

The TSH level comes back high at 9 µU/ml (microunits per millilitre), but his free T4 is within the normal range. Because his doctor is unsure of what to do, he refers him to a specialist who tells Victor that he appears to have subclinical hypothyroidism, although he thinks the symptoms Victor describes are due to his thyroid, so it’s not really subclinical at all. He puts Victor on thyroid hormone replacement pills.

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After two weeks, Victor notices with relief that his bowel movements improve. He feels less tired and much less cold. Repeat thyroid function tests show his TSH is now 6 µU/ml (microunits per millilitre), which is still a little high, so his dose of thyroid hormone is increased. A month later, his TSH test is down in the normal range, and Victor states that he is now back to his normal, mildly constipated self.

Deciphering signs and symptoms

The diagnosis of hypothyroidism is so easily missed in the elderly because so many of the changes our bodies experience as we grow older are typical findings in hypothyroidism. Some of the most important include: ߜ Slowing of mental function

ߜ Slowing of physical function

ߜ Tendency to have a lower body temperature