Thyroid Disorders Hypothyroidism

When the production of thyroid hormone decreases below the normal body's need, the condition is referred to as hypothyroidism. Without enough thyroid hormone, the body becomes tired and run down. Every organ system slows—the brain slows down making it difficult to concentrate, the gut slows down causing constipation, and metabolism slows down causing weight gain. Although there are many different causes of an underactive thyroid gland, the resulting effect on the body is the same.

Many of the symptoms of hypothyroidism are very subtle and are experienced by people without thyroid disease. Thus, a lot of physicians overlook the symptoms of fatigue, weight gain and depression and attribute them to other causes. Physicians should check to see if thyroid disease is the cause of these everyday symptoms, because an underactive thyroid is very easy to treat. In addition, patients who are treated for hypothyroidism can regain full control of their lives and eliminate these symptoms entirely.

Causes

The most common cause of hypothyroidism in the United States is chronic autoimmune thyroiditis (Hashimoto's thyroiditis), a condition characterized by inflammation and damage to the thyroid tissue. Damage occurs because immune cells which usually fight off infection and colds, attack the body's own thyroid tissue instead.

• Autoimmune Diseases
  If you have other autoimmune diseases, you may also be at risk for Hashimoto's thyroiditis. Some common examples of these autoimmune diseases include rheumatoid arthritis (the immune cells attack the joints) and diabetes (the immune cells attack the pancreas which produces insulin). In fact, about 10% of patients with Type I or juvenile diabetes mellitus develop chronic thyroiditis during their life. If you are diabetic and have thyroid disease, the amount of insulin you need every day may change. It is therefore important for patients with diabetes to be checked for thyroid disease by routine thyroid function blood tests on a regular basis. Still other examples of autoimmune diseases include vitiligo (a skin condition in which patches of skin lose their color and become white), Addison's disease (a disorder of the adrenal glands), and pernicious anemia (a special form of low blood count).
• Lithium Medication
  You may also be at risk for an underactive thyroid if you are taking a prescription medication which has been shown to cause thyroid disease. For example, if you have a psychiatric disease called manic-depressive disorder and are being treated with lithium, you may be at risk. This drug can cause thyroid enlargement and an underproduction of thyroid hormone, resulting in hypothyroidism.
• Pregnancy
  Thyroiditis is especially common in the post partum period (it is also sometimes confused with postpartum depression) and may require thyroid hormone adjustments. It is also important to note that hypothyroidism (and hyperthyroidism) can sometimes cause unexplained infertility or miscarriages particularly early in pregnancy. Therefore, thyroid function tests are often a routine part of evaluating a patient who may have problems with pregnancy. In addition, during pregnancy, the requirements for thyroid hormone may increase, and should be monitored closely in the first and second trimester. Although some forms of thyroid disease may actually improve during pregnancy, pregnancy is also often associated with the development of benign thyroid disease.
• Aging
  As we age, hypothyroidism becomes increasingly common, particularly in women (10% of all women over the age of 50 show signs of a failing thyroid). Therefore, if you are older (or if after surgery your remaining thyroid lobe is diseased in some way), your thyroid (or remaining thyroid lobe) may not provide enough thyroid hormone, thus resulting in hypothyroidism.
• Surgery
  Whenever the thyroid gland is removed completely by surgery because of a thyroid disorder, hypothyroidism results and your doctor will prescribe thyroid hormone medication to make up for the hormone that body can no longer make itself. If you have only half of your thyroid removed (and the other half that is not removed is normal), you can still produce enough thyroid hormone from the remaining half of the thyroid in order to function normally. However, if you have had half of your thyroid removed, you need to have regular check-ups with your doctor for thyroid function blood tests in order to make sure that the remaining portion of the thyroid is functioning well. If it is not, you will need to start thyroid hormone medication.
• Radioactive Iodine
  Another common cause of hypothyroidism is the use of radioactive iodine. Some thyroid diseases such as Graves' disease (a form of hyperthyroidism) are treated with radioactive iodine. The radioactive iodine destroys the overactive thyroid cells, thus eliminating the source of the excess thyroid hormone or hyperthyroidism. This destruction sometimes results in hypothyroidism. This type of hypothyroidism may be difficult to detect immediately, because there may be just a small amount of thyroid tissue that is not destroyed right away. This small piece of thyroid may produce enough thyroid hormone for the body for a little while. However, if this piece of thyroid burns out or gives up, hypothyroidism may result.
  
  Because this hypothyroidism can occur anywhere from months to years after treatment with radioactive iodine, you may not immediately recognize the subtle symptoms of fatigue, weight gain and difficulty concentrating. Therefore if you have been treated with therapeutic doses of radioactive iodine, you should visit your doctors regularly and have routine thyroid function blood tests. By checking these blood tests once a year, hypothyroidism may be discovered in its earliest stages before you develop symptoms like fatigue and weight gain.
• Secondary Hypothyroidism
  Finally, there are some rare causes of hypothyroidism related to brain diseases, also called secondary hypothyroidism. Disorders of the pituitary gland or hypothalamus portions of the brain may cause thyroid hormone deficiency in addition to other hormonal imbalances. This type of rare hypothyroidism can also be treated with thyroid hormone medication.

Symptoms

The symptoms of hypothyroidism are mainly dependent on the amount of decrease in thyroid hormone and duration of time that the decrease has been present. For most patients, the symptoms are mild and can often be confused with other problems. The symptoms may include the following:

Diagnosis

The most effective and efficient way to diagnose hypothyroidism is by measuring the blood TSH (Thyroid Stimulating Hormone) level. Additional tests which may be helpful in determining the etiology of hypothyroidism include thyroid hormone levels, thyroid biopsy, thyroid antibodies (antiperioxidases or antithyroglobulin), thyroid scan and sonogram.

Treatment and Management

Since hypothyroid patients are deficient in thyroid hormone, they are treated with hormone replacement drugs such as levothyroxine (Synthroid®). Although thyroid hormone drugs produce no allergic reactions or side-effects, their effectiveness may be decreased by patient age or by interactions with other drugs. Therefore, it is important that the physician is informed about any other medications the patient may be taking.

Once blood tests confirm that the patient is on the correct dose of medication, the frequency of office visits can be reduced. A follow-up in 6 months and then annually is a common schedule. During follow-up visits, an appropriate interim history and physical examination is performed along with appropriate tests.