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Thyroid Diseases Articles
Thyroidectomy is the surgical removal of part or all of the thyroid gland. This important gland, located in the lower front portion of the neck, produces thyroid hormone, which regulates the body's production of energy. A healthy thyroid gland is shaped like a butterfly, with right and left lobes connected by a bridge called the thyroid isthmus. Depending on the reason for a thyroidectomy, all or part of the thyroid gland will be removed.
Hyperthyroidism is a condition in which your body makes too much thyroid hormone. It is also called overactive thyroid.
Thyroid hormones are made by the thyroid gland. The thyroid gland is located in the lower front of the neck.
Thyroid hormones regulate the body's energy. When levels of thyroid hormones are unusually high, the body burns energy faster and many vital functions speed up.
Hyperthyroidism is usually caused by the thyroid gland producing too much thyroid hormone. The three most common reasons for this are:
Graves' disease. Graves' disease is the most common cause of hyperthyroidism. It is an immune system disorder. The body produces antibodies that cause the thyroid to make and release too much thyroid hormone. If you have a relative with Graves' disease, you have an increased risk of developing hyperthyroidism.
Thyroid tumor. A noncancerous thyroid tumor may make and secrete increased amounts of thyroid hormones.
Toxic multinodular goiter. The thyroid gland is enlarged with many noncancerous thyroid tumors. They secrete increased amounts of thyroid hormone.
Thyroid cancer is the uncontrolled growth of abnormal cells in the thyroid gland. The thyroid gland is shaped like a butterfly. It is located under the Adam's apple in the front of the neck. Most cases of thyroid cancer can be cured.
One of the functions of the thyroid gland is to make thyroid hormone, which requires iodine. The gland collects iodine from foods, concentrates it, and produces thyroid hormone. Doctors often exploit this important function when treating thyroid cancer.
Thyroid hormone helps regulate the body's metabolism and energy level. An overactive thyroid can lead to hyperactivity, the "jitters," and an irregular heart rhythm; an underactive thyroid, fatigue and sluggishness. Cancer can affect the thyroid and cause these changes.
Hypothyroidism means your thyroid gland cannot produce the normal amount of thyroid hormone. Your thyroid gland is under active. The thyroid gland is located in the lower, front of the neck.
Thyroid hormones regulate the body's energy. When levels of thyroid hormones are abnormally low, the body burns energy more slowly, and vital functions, such as heartbeat and temperature regulation, slow down. Causes of hypothyroidism include:
Thyroid surgery or radioiodine ablation treatments to treat thyroid cancer or hyperthyroidism (abnormally high levels of thyroid hormones)
An autoimmune disorder, in which the body's own immune system attacks the thyroid
An inborn (congenital) thyroid defect
Short-term hypothyroidism can be caused by certain types of thyroid inflammation or thyroid infections with a virus. In less than 5% of cases, hypothyroidism is caused by a problem with the hypothalamus or a pituitary gland rather than the thyroid gland. The hypothalamus is a brain structure that normally signals the pituitary gland to make thyroid stimulating hormone (TSH), which causes the thyroid to make thyroid hormones.
Parathyroid cancer is a very rare cancer that develops in the parathyroid glands. A pair of these pea-sized glands sits next to the thyroid on either side of the front of the neck.
The four parathyroid glands produce parathyroid hormone (PTH). This chemical
raises calcium levels in the blood by forcing the bones to release calcium
stimulates the intestines to absorb more calcium from food
signals the kidneys to withhold calcium from the urine.
Healthy parathyroid glands adjust their production of PTH to keep blood calcium levels within a normal range.
When parathyroid cells become cancerous, they multiply out of control. They usually form a firm, grayish-white tumor. The tumor can invade the thyroid gland and neck muscles.
As the cancerous cells grow, they usually produce too much PTH. This causes abnormally high levels of calcium in the blood (hypercalcemia). PTH can get so high that the bones pour out too much calcium. This can cause bone pain and lead to osteoporosis (thin, brittle bones).
Elevated levels of PTH also force the kidneys to retain large amounts of calcium, triggering the formation of kidney stones. Very high calcium can also cause kidney damage, dehydration, and confusion.
Parathyroid cancer usually occurs in adults in their 50s and 60s. Because it is so rare, researchers have not determined whether specific environmental or lifestyle factors increase the risk of this cancer. Some cases seem to have a genetic link, with several generations of a single family affected.
There are two types of thyroid nuclear medicine tests. Both assess the health of your thyroid, a gland in your neck. The first type, a thyroid scan, produces a picture of the gland. It can spot lumps or inflammation, or to investigate the cause of an overactive thyroid. The second type, a radioactive iodine uptake test, is performed to see if your thyroid is functioning normally and to determine why thyroid hormone levels may be elevated. For both types of test, a small amount of a weakly radioactive substance, known as a radionuclide, is either injected into a vein or given to you as a pill.
Hypoparathyroidism is a rare disorder in which the body produces too little or no parathyroid hormone. This hormone, together with vitamin D and another hormone called calcitonin, regulates the amount of calcium in the blood. Hypoparathyroidism can result in an abnormally low level of calcium in the blood, called hypocalcemia.
Parathyroid hormone is produced by the parathyroid glands, four small glands located behind the thyroid gland in the neck.
Doctors classify hypoparathyroidism as either hereditary or acquired. In hereditary hypoparathyroidism, the parathyroid glands are either absent at birth or fail to function properly for some unknown reason. Hereditary hypoparathyroidism sometimes occurs with other developmental defects, or as part of a syndrome that affects the thyroid gland and adrenal cortex. It generally causes symptoms before age 10, although occasionally symptoms will appear later.
Acquired hypoparathyroidism most commonly occurs when the parathyroid glands are removed or damaged during surgery. This can occur during surgery on the thyroid gland to treat hyperthyroidism or a thyroid tumor or during surgery on the parathyroid glands themselves to treat an overproduction of parathyroid hormone (hyperparathyroidism). The acquired hypoparathyroidism is most often temporary. Acquired hypoparathyroidism is less common than it once was because surgeons have recognized the importance of preserving the parathyroid glands during surgery and because nonsurgical treatments for hyperthyroidism have become more common.
For decades, Levothyroxine sodium, the most popular thyroid hormone for replacement therapy, had not been required to go through the Food and Drug Administration's approval process. But in 1997, the FDA reclassified all oral levothyroxine products as "new drugs," obligating the manufacturers to meet approved New Drug Applications (NDAs) before August 14, 2001. A history of potency and stability problems with orally administered levothyroxine sodium products resulted in the agency's decision.Two levothyroxine sodium products, Unithroid and Levoxyl, have recently been approved by the FDA to treat hypothyroidism. And now the FDA is issuing guidance regarding the transition of patients from unapproved to these approved products, and the handling of those products being marketed without an approved application. The FDA will gradually do away with the unapproved products to allow manufacturers of approved products to expand to meet demand and to give patients and health care providers enough time for a clean transition.Two of the most common formulations that are being phased out are Synthroid and Levothroid. Manufacturers of unapproved oral levothyroxine sodium drug products without an NDA pending with the FDA must cease distribution by August 14, 2001.August 2001 Update
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Graves' disease is the most common cause of hyperthyroidism, an overactivity of the thyroid gland that results in too much thyroid hormone circulating through the body. The high thyroid level raises the body's metabolism, causing frequent bowel movements, increased heart rate, irritability, and anxiety, as well as an increased appetite partnered with weight loss. In addition, about one in five people with Graves' disease has bulging eyes. The condition is most common in young to middle-aged women.Doctors usually treat Graves' disease with antithyroid medicines, radioactive iodine treatment, or surgery. The goal of treatment is to induce long-term remission, that is, to permanently reduce the amount of hormone the thyroid gland produces. Most often, patients find antithyroid medicines effective while they are on them, but hyperthyroidism often returns once the drugs are stopped. Radioactive iodine and surgery, on the other hand, destroy or remove so much of the thyroid gland that it no longer produces enough thyroid hormone. As a result, patients need to take thyroid pills for the rest of their lives. Until now, it has been difficult for physicians to predict which treatment will be more effective for which patients.A new study, published in the March 2000 The Journal of Clinical Endocrinology & Metabolism, shows that patients under 40 and men do not respond as well to antithyroid medicines, and that men are less likely to be successfully treated with only one dose of radioiodine therapy. The researchers followed 423 patients for six months after they completed therapy. Of the patients, 314 received antithyroid medicines (usually an 18-month course of carbimazole) and 109 received radioiodine therapy.Of the patients taking antithyroid medicines, only 37% remained in remission six months after treatment. Of those, men were significantly less likely than women (20% vs. 40%) to remain in remission, and patients younger than 40 were significantly less likely than patients over 40 (33% vs. 48%) to stay in remission. Men were also significantly less likely than women (47% vs. 74%) to enter remission after one dose of radioiodine therapy.In response to these findings, the researchers proposed that men and patients younger than 40 receive early treatment with radioiodine therapy or surgery, since antithyroid medicines are unlikely to lead to remission. In addition, they suggest further research to investigate whether higher initial doses of radioiodine may be appropriate for male patients.To learn more about Graves' disease, see page 844 of the Family Health Guide.