Thyroid for Dummies (16 page)

ߜ Surgery can damage one or both nerves supplying the voice box (
recurrent laryngeal nerves
), which can lead to hoarseness or permanent damage to the voice.

ߜ Surgery can damage the
parathyroid glands
that lie behind the thyroid, leading to a severe drop in blood calcium.

ߜ Although a surgeon’s goal is sometimes to leave enough thyroid tissue to keep the patient’s thyroid function normal, low thyroid function may begin immediately after surgery or develop during the next few years.

These days, most surgery is designed to remove the whole thyroid gland (total thyroidectomy).

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ߜ If someone has had previous neck surgery, attempting another operation is risky as important nerves and arteries may be tangled up in scar tissue.

ߜ In people with hyperthyroidism who have only part of their thyroid gland removed during surgery, 10 per cent have a relapse and develop hyperthyroidism again over a period of ten years.

Some specialists believe that surgery releases thyroid antigens (tissue or chemicals to which the body is not normally exposed) into the blood stream and, where a lot of thyroid tissue is left intact, this can worsen the autoimmune condition, possibly resulting in worse eye disease. Whether or not this belief is true is unclear.

For more information about thyroid surgery, see Chapter 13.

Radioactive iodine treatment

In this treatment, a person swallows a capsule containing radioactive iodine (RAI). Because the thyroid uses more iodine than any other organ or gland in the body, the RAI quickly concentrates in the thyroid and releases enough radiation to slowly destroy the overactive thyroid cells.

Radioactive iodine is an ideal solution to the problem of hyperthyroidism.

Decades of experience with radioactive iodine have lain to rest a number of the fears surrounding this treatment:

ߜ Studies report no increase in thyroid cancer in adults who receive RAI, or of cancer elsewhere in the body.

ߜ Studies report no increase in cases of leukaemia after RAI.

ߜ RAI does not affect fertility.

ߜ Children of mothers who previously received RAI have normal thyroid function and no congenital defects at birth (though RAI is never given during a pregnancy). These children can, however, still develop Graves’

disease later in life because it is hereditary.

In addition, RAI is inexpensive and avoids the risks of surgery. But RAI does have its share of drawbacks:

ߜ RAI is not suitable for a pregnant woman because the drug crosses the placenta and enters the baby’s thyroid, possibly destroying it.

ߜ RAI is not suitable for use in small children (younger than teenagers) because of the incidence of thyroid cancer when small children (whose thyroid gland is still developing) are exposed to it. (For example, thyroid cancer was rampant among children exposed to RAI outside the Russian nuclear plant at Chernobyl.)

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ߜ Finding the exact dose to cure the hyperthyroidism but leave the patient with normal thyroid function is impossible. If too little RAI is used, another treatment is needed. Most patients given enough RAI to cure their hyperthyroidism do eventually become hypothyroid (usually within three to six months) and need to take thyroid hormone replacement for life. The likelihood of developing hypothyroidism RAI is low if the hyperthyroidism is due to toxic multinodular goitre, or to a toxic nodule, however.

ߜ If RAI causes hypothyroidism, patients may experience three unusual symptoms: joint aches, stiffness, and headaches. The headaches are possibly due to swelling of the pituitary gland.

ߜ By slowly destroying the thyroid, RAI releases a large amount of thyroid antigens into the patient’s circulation (similar to the situation with surgery), which may greatly increase autoimmunity and make eye disease worse.

ߜ People receiving RAI need follow-up blood tests for years to monitor for the development of hypothyroidism.

After RAI is given, it takes about three weeks to start having an effect, and the maximal effect occurs about two months after treatment. These timeframes can vary depending on how large the gland is when the treatment occurs, however.

Antithyroid pills

In the United Kingdom, there are two antithyroid pills used to control hyperthyroidism, propylthiouracil (PTU) and carbimazole. Both pills block the production of thyroid hormones, but propylthiouracil also blocks the conversion of T4 to T3, giving it a theoretical advantage over carbimazole. This advantage doesn’t seem to matter much in practise unless you are trying to control the hyperthyroidism very rapidly and, overall, carbimazole is more widely used in the United Kingdom.

A major advantage of these pills is that, unlike surgery or radioactive iodine, they help to treat all complications of Graves’ disease, including eye disease, as they reduce autoimmunity. Also, given in correct dosages, they do not lead to hypothyroidism.

When either drug is given, the patient usually starts to feel better after three weeks, and the hyperthyroidism is controlled within six weeks. Then, it is important to monitor the patient’s free T4 level at least every six to eight weeks, because treatment can lower T4 into the hypothyroid range.

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Two different treatment regimens are used:

ߜ A titration regime that adjusts doses up and down to try to achieve a normal (euthyroid) state.

ߜ A block-replace regime in which the antithyroid drug is designed to totally block thyroid, with T4 replaced as a tablet. This regime has the advantage of avoiding hypothyroidism and the need for frequent blood tests to check for hypothyroidism. This method is not suitable during pregnancy.

Neither regime has a clear advantage over the other in terms of outcome.

Research suggests that the best length of time for someone to receive the titration regime is 12–18 months, and for the block-replace regime, 6–12

months. People often relapse when treatment is stopped, however. On average, around one-third of people taking antithyroid pills remain under control after they stop taking the propylthiouracil or carbimazole. The people most likely to achieve remission with one of these regimes are those with mild disease and small goitres. For the other two-thirds, the symptoms of hyperthyroidism recur after the pills are stopped. These people can choose to continue on antithyroid drugs or to receive another treatment – either surgery or RAI.

Most people taking an antithyroid drug start on 15–40 mg (milligrams) of carbimazole once a day, while initial doses of propylthiouracil range from 200–400 mg per day divided into three daily doses. As thyroid function returns to normal, after 4–8 weeks, the doctor decides which of the two regimes to use. In the titration regime, the daily dose of drug is gradually reduced to a maintenance dose of 5–15 mg per day for carbimazole, or 50–

150 mg per day for propylthiouracil. Regular blood tests help to decide what the best maintenance dose is for an individual person. If the block-replace regime is used, then thyroid hormone replacement is simply added in and the antithyroid drug is kept at its previous higher level.

Like surgery and RAI, antithyroid drugs carry some risks. The major risk is that they can cause a reduction in white blood cells and even, very rarely, a complete lack of white blood cell production (a condition called
agranulocytosis
). If 10,000 people take an antithyroid drug for one year, then just three develop this problem. Although this condition usually occurs within the first three months of treatment, in people taking especially large doses of medication, the condition is occasionally seen later on and at low doses. This problem goes away when the person stops taking the drug.

One way to avoid severe loss of white blood cell production is to have a white cell count done each time you visit your doctor while you are on these pills.

If you are on carbimazole or propylthiouracil and develop a fever, sore throat, mouth ulcers, or other symptoms of infection stop taking the antithyroid drug and see your doctor for an urgent blood test to see whether you just have a cold or whether you’ve developed a low white blood cell count.

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Some people taking antithyroid drugs develop skin rashes and itching. If relatively mild, these symptoms are treated with an antihistamine without having to stop treatment. Alternatively, if you are taking carbimazole your doctor may switch you to propylthiouracil or the other way round.

Another rare side effect of these drugs is the occurrence of liver function abnormalities and even liver damage. If you take one of these drugs, ask your doctor to check your liver function every few surgery visits.

Other helpful medications

A class of pills called beta-blockers can reduce the symptoms of hyperthyroidism without actually treating the condition. Beta-blockers are valuable for controlling the disease while antithyroid pills or radioactive iodine have a chance to work. They are also prescribed by family doctors to reduce symptoms in people with hyperthyroidism who are waiting to see a hospital specialist for the first time. The most commonly used beta-blocker drugs are propranolol and metoprolol, which help to slow the heart, decrease anxiety, and reduce tremor. Because the liver works more quickly to break down these drugs in people with an overactive thyroid, beta-blockers are taken more often than normal – three to four times a day. They are usually continued for a few weeks until the other medications take effect, or are used as preparation for surgery. In fact, beta-blockers are often the only treatment needed for someone with hyperthyroidism due to thyroiditis.

People with heart failure as a result of severe hyperthyroidism are given different beta-blockers (bisoprolol and carvedilol) as these drugs are licensed for use in heart failure and do not make the condition worse.

Preparations of iodine are also available for use to temporarily block thyroid hormone production and reduce the blood flowing to the thyroid in preparation for surgery.

Treating Other Causes of Hyperthyroidism

People who have hyperthyroidism that isn’t caused by Graves’ disease may need other treatment options:

ߜ People with factitious hyperthyroidism are advised to stop taking their thyroid pills and start some form of psychotherapy.

ߜ A thyroid with one or more nodules that produce too much thyroid hormone responds best to radioactive iodine (RAI); because the nodules are not caused by an autoimmune condition; thus, eliminating the concern about thyroid eye disease lingering after the treatment. In the case 11_031727 ch06.qxp 9/6/06 10:43 PM Page 80

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of a single nodule causing the hyperthyroidism, the nodule is eliminated with RAI, and the rest of the thyroid often returns to normal function.

When single or multiple overactive nodules are present, antithyroid drugs almost never cause a permanent remission.

ߜ T3 thyrotoxicosis responds to antithyroid medication just like Graves’

disease due to excess T4.

ߜ The hyperthyroid phase of subacute thyroiditis does not last very long.

If necessary, the beta-blocker propranolol can control symptoms until the hyperthyroidism subsides.

ߜ When symptoms are due to a choriocarcinoma making hormones that stimulate the thyroid, the tumour is always removed.

ߜ A tumour in the brain causing excessive production of thyroid-stimulating hormone must be treated by surgery or radiation therapy.

Surviving Thyroid Storm

Severe hyperthyroidism, known as
thyroid storm
, is a rare condition that is sometimes fatal. The clinical picture is one of extreme signs and symptoms of hyperthyroidism. The person affected has a high fever and a very rapid heartbeat. The person may vomit, have diarrhoea, and often be dehydrated.

They may develop heart failure and have a heart rhythm that is difficult to control. The person can lapse into delirium or even a coma.

Fortunately, thyroid storm is rarely seen because hyperthyroidism is almost always diagnosed at a much earlier stage. The condition is sometimes seen when partially controlled hyperthyroidism is complicated with an added infection. When this state does occur, rapid treatment is essential.

This condition is a true medical emergency and admission to intensive care is vital, as the person needs careful management from a physician who is very aware of the treatment of severe hyperthyroidism.

The doctor usually starts a number of treatments all at once. The patient is given fluids, one of the antithyroid drugs (such as propylthiouracil), potassium iodide, steroids, and a beta-blocker like propranolol. This combination of medication can lower the level of T3 hormone to normal in a day, although the patient takes many more days to fully recover.

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Chapter 7

Getting the Low-Down

on Thyroid Nodules

In This Chapter

ᮣ Defining a thyroid nodule

ᮣ Determining whether a nodule is cancer

ᮣ Performing thyroid surgery

ᮣ Treating benign nodules

In some ways, the thyroid is a bit of an annoying gland as it has a tendency to keep forming bumps and growths that are of little or no significance.

Even so, these thyroid lumps are always fully evaluated by your specialist just in case they prove cancerous – although thyroid cancer is rarely fatal (see Chapter 8). As this gland causes so much trouble, surgeons often feel that they’d love to simply get rid of the thyroid, similar to the way in which they used to fling out misbehaving tonsils and adenoids. However, the thyroid is so important to our health that they usually do their best to give this bit of

‘pain in the neck’ tissue a reprieve.