Hyperthyroidism Part 2

Graves' disease

Graves' disease, which is caused by a generalized overactivity of the thyroid gland, and is the most common cause of hyperthyroidism. In this condition, the thyroid gland usually has lost the ability to respond to the normal control by the pituitary gland via TSH (renegade). Graves' disease is hereditary and is up to five times more common among women than men.

Graves' disease is thought to be an autoimmune disease, and antibodies that are characteristic of the illness may be found in the blood. These antibodies include thyroid stimulating immunoglobulin (TSI antibodies), thyroid peroxidase antibodies (TPO), and TSH receptor antibodies.

Graves' disease symptoms and signs:

Signs and symptoms of Graves’ disease include those of hyperthyroidism; however, Graves’ disease may be associated with eye disease (Graves' opthalmopathy) and skin lesions (dermopathy). 
Opthalmopathy can occur before, after, or at the same time as the hyperthyroidism. Early on, it may cause sensitivity to light and a feeling of "sand in the eyes." The eyes may be reddened and produce excess tears. Swelling behind the eyeballs causes the eyes to protrude, and double vision can occur. The degree of opthalmopathy is worsened in those who smoke.

In addition to the symptoms of hyperthyroidism mentioned above, Grave's disease may be associated with eye disease (Graves' opthalmopathy) and skin lesions (dermopathy). 

The course of the eye disease is often independent of the thyroid disease, and steroid medications may be necessary to control the inflammation that causes the opthalmopathy. In addition, surgical intervention may be required. The skin condition (dermopathy) is rare and causes a painless, red, lumpy skin rash on the front of the legs.

Graves' disease triggers

The triggers for Graves' disease include:

• stress,
• smoking,
• radiation to the neck,
• medications, and
• infectious organisms such as viruses.

Graves' disease can be diagnosed by a standard, nuclear medicine thyroid scan, which shows diffusely increased uptake of a radioactively labeled iodine. In addition, a blood test may reveal elevated TSI levels.

Thyroiditis (thyroid gland inflammation)

Inflammation of the thyroid gland may occur after a viral illness (subacute thyroiditis). This condition is associated with signs and symptoms of fever and sore throat , often with painful swallowing. The thyroid gland is also tender to touch. There may be generalized neck aches and pains. Inflammation of the gland with an accumulation of white blood cells known as lymphocytes (lymphocytic thyroiditis) may also occur. In both of these conditions, the inflammation leaves the thyroid gland "leaky," so that the amount of thyroid hormone entering the blood is increased. Lymphocytic thyroiditis is most common after a pregnancy and can actually occur in up to 8% of women after delivery. In these cases, the hyperthyroid phase can last from 4 to 12 weeks and is often followed by a hypothyroid (low thyroid output) phase that can last for up to 6 months. The majority of affected women return to a state of normal thyroid function. 

Thyroiditis is inflammation of your thyroid that causes stored thyroid hormone to leak out of your thyroid gland. The hyperthyroidism may last for up to 3 months, after which your thyroid may become underactive, a condition called hypothyroidism. The hypothyroidism usually lasts 12 to 18 months, but sometimes is permanent.

Several types of thyroiditis can cause hyperthyroidism and then cause hypothyroidism:

·         Subacute thyroiditis. This condition involves a painfully inflamed and enlarged thyroid. Experts are not sure what causes subacute thyroiditis, but it may be related to an infection caused by a virus or bacteria.

·         Postpartum thyroiditis. This type of thyroiditis develops after a woman gives birth.

·         Silent thyroiditis. This type of thyroiditis is called “silent” because it is painless, even though your thyroid may be enlarged. Experts think silent thyroiditis is probably an autoimmune condition.

Too much iodine

Your thyroid uses iodine to make thyroid hormone. The amount of iodine you consume affects the amount of thyroid hormone your thyroid makes. In some people, consuming large amounts of iodine may cause the thyroid to make too much thyroid hormone.

Some medicines and cough syrups may contain a lot of iodine. One example is the heart medicine amiodarone. Seaweed and seaweed-based supplements also contain a lot of iodine.

Too much thyroid hormone medicine

Some people who take thyroid hormone medicine for hypothyroidism may take too much. If you take thyroid hormone medicine, you should see your doctor at least once a year to have your thyroid hormone levels checked. You may need to adjust your dose if your thyroid hormone level is too high.

Some other medicines may also interact with thyroid hormone medicine to raise hormone levels. If you take thyroid hormone medicine, ask your doctor about interactions when starting new medicines.

Other causes of hyperthyroidism

Functioning adenoma and toxic multinodular goiter

As we age, lumps or nodules may form in the thyroid gland. Usually, these lumps do not produce thyroid hormones and require no treatment. Occasionally, a nodule may become "autonomous," which means that it does not respond to pituitary regulation and produces thyroid hormones independently. This becomes more likely if the nodule is larger than 3 cm. When there is a single nodule that is independently producing thyroid hormones, it is called a functioning nodule. If there is more than one functioning nodule, the term toxic, multinodular goiter is used. Functioning nodules may be readily detected with a thyroid scan.

Excessive intake of thyroid hormones

Taking too much thyroid hormone medication is actually quite common. Excessive doses of thyroid hormones frequently go undetected due to the lack of follow-up of patients taking their thyroid medicine. Other persons may be abusing the drug in an attempt to achieve other goals such as weight loss.

Abnormal secretion of TSH

A tumor in the pituitary gland may produce an abnormally high secretion of TSH (the thyroid stimulating hormone produced by the pituitary gland). This leads to excessive signaling to the thyroid gland to produce thyroid hormones. This condition is very rare and can be associated with other abnormalities of the pituitary gland. To identify this disorder, an endocrinologist performs elaborate tests to assess the release of TSH.

Excessive iodine intake

The thyroid gland uses iodine to make thyroid hormones. An excess of iodine may cause hyperthyroidism. Iodine-induced hyperthyroidism is usually seen in patients who already have an underlying abnormal thyroid gland. Certain medications, such as amiodarone (Cordarone), which is used in the treatment of heart problems, contain a large amount of iodine and may be associated with thyroid function abnormalities.

What tests are used for the diagnosis of hyperthyroidism?

A blood test can confirm the diagnosis of hyperthyroidism. Usually, in hyperthyroidism or overactive thyroid, blood levels of thyroid hormones are elevated. However, there is one exception. If the excessive amount of thyroid hormone is due to a TSH-secreting pituitary tumor, then the levels of TSH will be abnormally high. This uncommon disease is known as "secondary hyperthyroidism."

Although the blood tests mentioned previously can confirm the presence of excessive thyroid hormone, they do not point to a specific cause. A combination of antibody screening (for Graves' disease) and a thyroid scan using radioactively labeled iodine (which concentrates in the thyroid gland) can help diagnose the underlying thyroid disease. Graves' disease is almost certain if there are obvious signs and symptoms that affect they eyes. Tests for hyperthyroidism are based on an individual basis.

Medications for hyperthyroidism treatment

The options for treating hyperthyroidism include, treating the symptoms of the condition with medications, antithyroid drugs, radioactive iodine, and surgery.

Medications that immediately treat hyperthyroidism symptoms caused by excessive thyroid hormones, such as a rapid heart rate, include beta-blockers, for example, propranolol (Inderal), atenolol(Tenormin), and metoprolol (Lopressor). A doctor determines which patients to treat based on a number of variables including the underlying cause of hyperthyroidism, the age of the patient, the size of the thyroid gland, and the presence of coexisting medical illnesses.

Medications for the treatment of hyperthyroidism symptoms and signs

There are medications available to immediately treat the symptoms caused by excessive thyroid hormones, such as a rapid heart rate. One of the main classes of drugs used to treat these symptoms is the beta-blockers [for example, propranolol (Inderal), atenolol (Tenormin), metoprolol (Lopressor)]. These medications counteract the effect of thyroid hormone to increase metabolism, but they do not alter the levels of thyroid hormones in the blood. A doctor determines which patients to treat based on a number of variables including the underlying cause of hyperthyroidism, the age of the patient, the size of the thyroid gland, and the presence of coexisting medical illnesses.

Antithyroid drugs

There are two main antithyroid drugs available for use in the United States to treat hyperthyroidism, methimazole (Tapazole) and propylthiouracil (PTU). The major risk of these medications is occasional suppression of production of white blood cells by the bone marrow (agranulocytosis). (White cells are needed to fight infection.) It is impossible to tell if or when this side effect is going to occur, so regular determination of white blood cells in the blood are not useful.

Rarely, methimazole or propylthiouracil may cause fever, sore throat, or other signs of infection. If you develop these symptoms, contact your doctor immediately.
Usually, long-term antithyroid therapy is only used for people with Graves' disease, since this disease may actually go into remission under treatment without requiring treatment with thyroid radiation or surgery. If treated from one to two years, data shows remission rates of 40%-70%. When the disease is in remission, the gland is no longer overactive, and antithyroid medication is not needed.

Studies also have shown that adding a pill of thyroid hormone to the antithyroid medication results in higher remission rates. This type of therapy remains controversial, however. When long-term therapy is withdrawn, patients should continue to be seen by the doctor every three months for the first year, since a relapse of Graves' disease is most likely in this time. If a patient does relapse, antithyroid drug therapy can be restarted, or radioactive iodine or surgery may be considered.

Radioactive iodine

Radioactive iodine is given orally (either by pill or liquid) on a one-time basis to ablate a hyperactive gland. The iodine given for ablative treatment is different from the iodine used in a scan. Radioactive iodine is given after a routine iodine scan, and uptake of the iodine is determined to confirm hyperthyroidism. There are no widespread side effects with this therapy.

Usually, more than 80% of patients are cured with a single dose of radioactive iodine. It takes between 8 to 12 weeks for the thyroid to become normal after therapy. Permanent hypothyroidism is the major complication of this form of treatment. While a temporary hypothyroid state may be seen up to six months after treatment with radioactive iodine, if it persists longer than six months, thyroid replacement therapy usually is begun.

Thyroidectomy (hyperthyroidism surgery)

With the introduction of radioactive iodine therapy and antithyroid drugs, surgery for hyperthyroidism (thyroidectomy) is less common. When this therapy is necessary, it is used in:

• Pregnant women and children who have major adverse reactions to antithyroid medications.
• People with very large thyroid glands and in those who have symptoms stemming from compression of tissues adjacent to the thyroid, such as difficulty swallowing, hoarseness, and shortness of breath.

Partial thyroidectomy (removal of a portion of the thyroid gland) was once a common treatment for hyperthyroidism. The goal is to remove the thyroid tissue that was producing the excessive thyroid hormone. However, if too much tissue is removed, an inadequate production of thyroid hormone (hypothyroidism) may result. In this situation, thyroid replacement therapy is started.

The major complication of thyroid surgery is disruption of the surrounding tissue, including the nerves supplying the vocal cords and the four tiny glands in the neck that regulate calcium levels in the body (the parathyroid glands). Accidental removal of these glands may result in low calcium levels (hypercalcemia) and require calcium replacement therapy.

to be continued.....