Thyroid for Dummies (13 page)

ߜ Dry, cool skin that is puffy, pale, and yellowish

ߜ White patches of skin where pigment is lost (a condition called vitiligo) ߜ Brittle nails

ߜ Dry, brittle hair that tends to fall out excessively – especially loss of the outer third of the eyebrows

ߜ Swelling that does not retain an indentation, especially of the legs (this condition is known as brawny oedema)

ߜ Hoarseness and slow speech with a thickened tongue

ߜ Expressionless face

ߜ Slow reflexes

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People with hypothyroidism complain of many different symptoms, and each person has unique complaints. Among the most common are: ߜ Intolerance to cold

ߜ Tiredness and a need to sleep

ߜ Weakness

ߜ Pain and stiffness in the joints and muscles

ߜ Constipation

ߜ Increased menstrual flow

ߜ Trouble hearing and a ringing in the ears

ߜ Trouble seeing at night

The physician who sees someone with these signs and symptoms obtains several tests to confirm the diagnosis. The two test results essential to the diagnosis are:

ߜ A free thyroxine (FT4) level that is lower than normal ߜ A thyroid-stimulating hormone (TSH) level that is higher than normal Other tests that support the diagnosis include:

ߜ A mild anaemia (decrease in red blood cells)

ߜ An increased cholesterol count

ߜ Elevated levels of thyroid autoantibodies (if the patient has autoimmune hypothyroidism)

ߜ A blood glucose level that is lower than normal

After the diagnosis of hypothyroidism is made, the various causes of this condition are checked out, as many of them are reversible without treating the thyroid directly.

Confusing conditions

The signs and symptoms of hypothyroidism are fairly non-specific and are easily confused with the signs and symptoms of other common conditions.

The three major sources of confusion are menopause, normal ageing, and stress. All three are common occurrences for women, and men experience at least two out of the three (although some doctors also believe that the male menopause exists). You can see how a person with low thyroid function could easily neglect to check for that condition. This fact is a major reason 10_031727 ch05.qxp 9/6/06 10:46 PM Page 58

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why some doctors suggest routine thyroid testing starting at age 35 and continuing every five years thereafter, although this view is highly controversial as thyroid screening costs a lot of money.

Pinpointing the Causes of Hypothyroidism

The two most common causes of hypothyroidism are iodine deficiency and chronic thyroiditis. Although iodine deficiency is rare in Europe and the United States, it is very common throughout the rest of the world. See Chapter 12 for a more detailed discussion of this problem. As mentioned earlier in this chapter, chronic thyroiditis is an inherited condition that is diagnosed by checking the levels of thyroid autoantibodies in the blood.

In addition to these two causes of hypothyroidism, many other reasons for people becoming hypothyroid exist. The causes detailed in the following sections are normally ruled out before your doctor starts treating your condition with thyroid hormone replacement.

Removal of the thyroid

If your thyroid is removed because of cancer or an infection, or in the course of treatment for hyperthyroidism (see Chapter 6), you usually become hypothyroid. Only if some tissue is left behind does the thyroid possibly continue to function, although it’s unlikely to produce enough thyroid hormones to meet your needs.

Absence of brain hormones

Anything that destroys the
hypothalamus
(the part of the brain that secretes
thyrotrophin-releasing hormone (TRH)
) or the
pituitary gland
at the base of the brain (which secretes thyroid-stimulating hormone (TSH)) produces c
entral
hypothyroidism
– hypothyroidism originating in the control centre of the body, the brain. A trauma, infection, or infiltration (a replacement of brain tissue with other tissue, which can occur when a patient has cancer) can cause this type of destruction. The same result can occur if the pituitary is exposed to a destructive treatment that prevents the production and release of TSH, such as radiotherapy (radiation treatment) to the area of the pituitary gland.

If hypothyroidism is caused by a problem with the hypothalamus or pituitary, some of the signs and symptoms associated with chronic (autoimmune) thyroiditis are not found. In particular, hoarseness and a thickened tongue occur 10_031727 ch05.qxp 9/6/06 10:46 PM Page 59

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in autoimmune hypothyroidism but not in hypothyroidism associated with a lack of brain hormones. In addition, the thyroid is not usually enlarged in this instance, because TSH is not stimulating it (because the brain isn’t making TSH). Also, the person’s hair and skin are not coarse in this situation (but they are if the patient has autoimmune hypothyroidism).

Symptoms that result from a lack of other pituitary hormones also help to differentiate central hypothyroidism from failure of the thyroid gland. These include fine wrinkling of the skin of the face and a more pronounced loss of underarm, pubic, and facial hair.

Foods that cause hypothyroidism

Interestingly, many common foods can cause hypothyroidism if you eat them in sufficient quantities, especially if you have an iodine deficiency. These foods are called
goitrogens
because they can trigger enlargement of the thyroid (a goitre) as well as hypothyroidism. They block the conversion of T4 hormone to T3, the active form of thyroid hormone (refer to Chapter 3). Among the more common foods that cause this condition are:

ߜ Almonds

ߜ Brussel sprouts

ߜ Cabbage

ߜ Cauliflower

ߜ Corn

ߜ Kale

ߜ Turnips

If your condition is due to consuming these foods, simply removing them from your diet cures your hypothyroidism. Your thyroid takes three to six weeks to return to normal after you stop eating these foods.

Drugs that cause hypothyroidism

Many different medications cause hypothyroidism in the same way as the goitrogens listed in the previous section; they block the conversion of T4 to T3. The drugs most likely to trigger this condition include: ߜ Adrenal steroids like prednisone and hydrocortisone, which treat inflammation

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ߜ Amiodarone, a heart drug

ߜ Antithyroid drugs like propylthiouricil and carbimazole (see Chapter 6) ߜ Lithium, for psychiatric treatment

ߜ Propranolol, a beta-blocker (see Chapter 6)

Coexisting autoimmune diseases

Occasionally, someone with an autoimmune thyroid disease has other autoimmune conditions, many of which involve other glands of the body. For example, diabetes mellitus Type 1 sometimes occurs together with an autoimmune thyroid disease. The cause of the diabetes is the autoimmune destruction of the insulin-producing cells of the pancreas. Another example is Addison’s disease, in which autoimmune destruction of the adrenal gland takes place.

Addison’s disease is associated with severe fatigue and low blood pressure and is especially important to identify; giving thyroid hormone without adrenal hormone to such a patient is dangerous as they can collapse due to lack of adrenal hormones.

Autoimmune destruction of the ovaries in women, or the testicles in men, may also occur when someone has autoimmune thyroiditis. The result for women is failure to menstruate, and for men infertility and impotence.

Another gland that is sometimes affected by an autoimmune disease is the
parathyroid
(which actually consists of four parathyroid glands) sitting behind the thyroid in the neck. Loss of parathyroid function results in low blood calcium and the possibility of severe muscle spasms and psychological changes.

Some autoimmune diseases that affect the joints of the body are found together with autoimmune thyroiditis. Rheumatoid arthritis is the most common example, but other diseases such as
Sjögren’s syndrome
and
systemic lupus
erythematosus
are also diagnosed.

Lastly, the blood disease called pernicious anaemia is an autoimmune disease that accompanies autoimmune thyroiditis on occasion. In this condition, cells of the stomach that produce acid are destroyed by autoimmunity. The patient is unable to absorb vitamin B12 and develops an anaemia (low blood count) along with symptoms in the nervous system.

On occasion, when these diseases occur together, treatment of one of them treats the other at the same time. For example, treating the hypothyroidism with thyroid hormone may greatly improve the diabetes.

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Diagnosing Severe Hypothyroidism

Hypothyroidism is rarely seen in its severest form in the United Kingdom –

severe hypothyroidism is known as
thyroid storm
– but if the disease is left untreated and total thyroid failure occurs, the patient may die. The clinical picture that develops is one of extreme worsening of the signs and symptoms described earlier in the chapter. The skin becomes extremely dry and coarse, and the person’s hair falls out. The person may lose all their eyebrows (and sometimes their eyelashes), and their body temperature may fall to a low level. The person becomes less and less active and may lapse into a coma (called
myxoedema coma
) that can last for many days until they die of heart failure or infection. (The infection or heart disease may precipitate the myxoedema coma in the first place in an elderly person with very low thyroid function.)

Because food is absorbed extremely slowly in severe hypothyroidism, treatment may require injections of thyroid hormones (described in the next section). (See Chapter 6 for more on thyroid storm.)

Treating Hypothyroidism

The treatment of hypothyroidism was once considered very complicated, but is now fairly simple after a diagnosis is made. However, a number of newer thoughts on the subject are worth considering as you and your doctor discuss treatment.

Taking the right hormones

People with hypothyroidism due to chronic thyroiditis, or because of the removal of the thyroid, have to take daily thyroid hormone replacement pills.

The first treatment to replace absent thyroid hormone came from the thyroids of animals and was called
desiccated thyroid
. For many decades, this type of hormone replacement was the only treatment available.

When making T4 hormone in the laboratory became possible, T4 (also called
L-thyroxine
) quickly replaced desiccated thyroid. This change was made for several reasons. First, the amount of hormone in a given animal’s thyroid differs from animal to animal, so the dose delivered varies considerably. Second, desiccated thyroid contains both T4 and T3 in amounts that are significantly different from the way it’s secreted by the normal thyroid gland (check out Chapter 3).

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For many years, doctors suspected that generic forms of thyroid hormone replacement pills (ones without a brand name) did not consistently provide a known level of the hormone, so doctors recommended brand name products so each person received exactly the same name of tablet with each prescription. Recent studies show that generic thyroid hormone has the same potency as brand name thyroid hormone and is, of course, much cheaper.

Because 80 per cent of the T3 thyroid hormone in your body comes from the conversion of T4 into T3 (at sites other than the thyroid), doctors usually give T4 alone and the body normally takes care of producing the T3 it needs.

Some recent studies show that when the human thyroid releases thyroid hormone, about 10 per cent is T3 (and the rest is T4). As a result, researchers wonder whether some people with hypothyroidism who take a mixture of T3 and T4 replacement hormone may feel better than those given T4 alone.

Several studies involving combination treatment with T4 and T3 have been published in medical journals, including the
Journal of Clinical Endocrinology
and Metabolism
(the foremost peer reviewed publication in the field of Endocrinology), as well as the
Journal of the American Medical Association
.

According to the British Thyroid Association (see Appendix B), the overall conclusion from these recent studies is that people taking combination therapy do not do any better than those taking T4 alone. In fact, some studies show a detrimental effect on psychological function with combination therapy.

However, doctors are keeping an open mind about combination therapy, and as new evidence becomes available, current opinions may change.

At present, however, almost all people in the world who are currently receiving replacement thyroid hormone to treat hypothyroidism are taking T4 alone.

But people have every right to receive a treatment they wish to try, as long as it’s legal. So, if you’re receiving T4 and still do not feel right, ask your doctor about taking both T3 and T4 together. Your doctor can review the latest evidence and consider whether or not the combination is likely to help you.

If the cause of your hypothyroidism is something other than autoimmune failure of your thyroid, or removal of your thyroid, the underlying cause is also dealt with at the same time as you take thyroid hormone replacement.

For example, if you have a pituitary tumour that is responsible for a loss of TSH, the tumour is treated, and any other hormones that are deficient are replaced in addition to thyroid hormones. If your hypothyroidism is caused by a drug or food, removal of that drug or food usually cures the condition.

However, sometimes you must continue to take the culprit drug, if no suitable alternative exists. In this case, your doctor prescribes thyroid hormone replacement to alleviate the hypothyroidism for as long as you continue to take the medication.