Monday, May 29, 2006

thyroid symptoms: Thyroid cancer

Thyroid cancer Definition

Thyroid cancer is a disease in which the thyroid cells become abnormal, grow uncontrollably, and form tumors. Thyroid cancers are grouped into four types, based on how the cell appears under the microscope. If left untreated, the cancer can spread to other parts of the body.

The thyroid is a butterfly-shaped gland, located at the base of the throat. It has two lobes, the left and the right. The thyroid gland makes hormones that regulate heart rate, blood pressure, body temperature, and metabolism. The hormones produced by the thyroid also affect the nervous system, muscles, and other organs, and play an important role in regulating childhood growth and development. The thyroid uses iodine, a mineral found in some foods, to make several of its hormones.

Diseases of the thyroid gland occur frequently, affecting millions of Americans. The most common diseases are an overactive or an underactive thyroid gland. These conditions are called hyperthyroidism (Grave's disease) or hypothyroidism. Sometimes, lumps or masses may develop in the thyroid glands. Ninety-five percent of these lumps or nodules are non-cancerous (benign), but all thyroid lumps should be taken seriously.

According to the estimates of the American Cancer Society, approximately 17,200 new cases of thyroid cancer will occur in the United States in 1998. This disease accounts for 1% of all cancers.

A woman's risk of developing thyroid cancer is three times greater than a man's. Most people who develop thyroid cancer are 50 years of age or older, but the disease can affect teenagers and young adults.

Thyroid cancers are grouped into four types, depending on how the cells look under the microscope. The types are papillary, follicular, medullary, and anaplastic thyroid cancers. The cancers grow at different rates, so the aggressiveness of each cancer is different.

Papillary cancer develops in the cells that produce thyroid hormones containing iodine. It is a slow-growing cancer and can be treated successfully. About 60-80% of all thyroid cancers are papillary cancers.

Follicular cancers also develop in the cells that produce iodine-containing hormones. Many of the follicular cancers have a good cure rate, but if the cancer invades blood vessels or grows into nearby structures in the neck, it may be difficult to control. About 30-50% of thyroid cancers are follicular cancers.

Medullary cancers develop in the parafollicular cells (also known as the C cells). These cells produce a hormone called calcitonin, which does not contain iodine. These cancers are more difficult to control because they have a tendency to spread to other parts of the body. About 5-7% of all thyroid cancers are medullary cancers. Approximately 7% of medullary cancers are caused by the alteration (mutation) of a gene called the RET gene; these cancers can be passed on in families.

Anaplastic cancer is the fastest growing of all thyroid cancers. The cells rapidly spread to the different parts of the body. About 2% of all thyroid cancers are anaplastic cancers.

thyroid Causes & symptoms

Although the exact cause of thyroid cancer has not yet been determined, it has been observed that thyroid cancer affects women three times as often as it affects men. The rate of thyroid cancer is also higher in whites than in African Americans.

Exposure to radiation during childhood is a known risk factor for thyroid cancer. In the 1950s and 1960s, radiation was used to treat acne and to reduce swelling and infection of organs in the neck, such as the tonsils, adenoids, and lymph nodes. Recent studies have proved that people who received radiation to the head and neck during their childhood have a higher than average chance of developing thyroid cancer.

In areas of the world where people's diets are low in iodine, papillary and follicular cancers occur more frequently. In the United States, dietary iodine is plentiful because it is added to table salt and other foods.

The most frequent symptom of thyroid cancer is a lump or nodule that can be felt in the neck. Other symptoms are rare. The lump usually is not painful, but some patients experience a tight or full feeling in the neck and have some difficulty breathing or swallowing. The lymph nodes may be swollen and the voice may become hoarse because the tumor presses on the nerves leading to the voice box.
Encyclopedia of Medicine by Lata Cherath

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