The Thyroid Gland

The thyroid gland is an organ that is considered to be part of the endocrine system. The endocrine system is made up of a number of different glands situated in different locations in the body. These glands function to produce biochemical substances called hormones that enter the bloodstream and travel throughout the body. Most of these hormones exert different effects in different tissues throughout the body to help regulate the metabolism, chemical balance, and reproductive function of the body. Other glands that make up the endocrine system include the pituitary gland, the parathyroid glands, the adrenal glands, the ovaries, the testicles, and the pancreas.

Where is it located?

The thyroid gland is located in the lower front part of the neck, just below the Adam\'s apple and above the top edge of the breastbone. It is made up of two lobes which are designated as the right lobe and the left lobe. These lobes are connected by a narrow band called the isthmus. A thin band of tissue called the pyramidal lobe extends upward from the isthmus. The overall configuration resembles a butterfly with the lobes representing the two wings. The thyroid gland wraps around portions of the larynx (voice box) and trachea (windpipe) that pass through the lower front part of the neck. The lobes are usually tucked behind the angular muscles in the neck that are connected to the top edge of the breastbone. It is usually difficult to see the outlines of the thyroid gland beneath the skin, though they may become more apparent if there is enlargement of one or both lobes.

What does it do?

The thyroid gland functions to produce thyroid hormone, a biochemical substance that enters the bloodstream and travels throughout the body to exert effects in a number of different organs and tissues. Thyroid hormone helps to regulate the body temperature and the overall rate of metabolism and energy expenditure. It also helps to maintain normal functioning of the cardiovascular system and the central nervous system.

The thyroid produces several hormones, of which two are key: triiodothyronine (T3) and thyroxine (T4).

The thyroid has cells that are the only cells in the body's capable of absorbing iodine. The thyroid takes in the iodine, obtained through food, iodized salt, or supplements, and combines that iodine with the amino acid tyrosine. The thyroid then converts the iodine/tyrosine combination into the hormones T3 and T4. The "3" and the "4" refer to the number of iodine molecules in each thyroid hormone molecule.

When it's in good condition, of all the hormone produced by your thyroid, 80% will be T4 and 20% T3. T3 is considered the biologically more active hormone -- the one that actually functions at the cellular level -- and is also considered several times stronger than T4.

Once released by the thyroid, the T3 and T4 travel through the bloodstream. The purpose is to help cells convert oxygen and calories into energy.

As mentioned, the thyroid produces some T3. But the rest of the T3 needed by the body is actually formed from the mostly inactive T4 by a process sometimes referred to as "T4 to T3 conversion." This conversion of T4 to T3 can take place in some organs other than the thyroid, including the hypothalamus, a part of your brain.

The thyroid is part of a huge feedback process. The hypothalamus in the brain releases something called Thyrotropin-releasing Hormone (TRH). The release of TRH tells the pituitary gland to release something called Thyroid Stimulating Hormone (TSH). This TSH, circulating in your bloodstream, is what tells the thyroid to make thyroid hormones and release them into your bloodstream.

in other words the thyroid gland works like an air conditioner. If there are enough thyroid hormones in the blood, the gland stops making the hormones (just as an air conditioner cycles off when there is enough cool air in a house). When the body needs more thyroid hormones, the gland starts producing again.
The pituitary gland works like a thermostat, telling the thyroid when to start and stop. The pituitary sends thyroid stimulating hormone (TSH) to the thyroid to tell the gland what to do.

Thyroid Disorders:

More than 10 million Americans have been diagnosed with thyroid disease, and another 13 million people are estimated to have undiagnosed thyroid problems in the U.S. alone. Frequently misunderstood, and far too often overlooked and misdiagnosed, thyroid disease can affect almost every aspect of health, so understanding more about the thyroid, and the symptoms that occur when something goes wrong with this small gland, can help you protect or regain good health health.

A February, 2000 research study found that the estimated number of people with undiagnosed thyroid disease may be 10 percent -- a level that is double what was previously thought. This may mean as many as 13 million Americans are currently undiagnosed. For women, the risk is even higher. A woman faces as high as a one in five chance of developing thyroid problems during her lifetime. That risk increases with age and for those with a family history of thyroid problems.

What are the different types of thyroid disorders?

Thyroid disorders include:

Hypothyroidism (underactive thyroid). This is the most common type of thyroid disorder, where the thyroid makes too little of the thyroid hormone that your body needs to function properly. It is most often caused by Hashimoto's disease. With this disease, the body's immune system (which normally protects you from disease) thinks the thyroid is a foreign invader and tries to destroy the thyroid. When damage is done to the thyroid, it can become larger (called goiter). Not getting enough iodine in a person's diet can also cause hypothyroidism, but this is more common outside of the United States (in the U.S., many products such as salt and bread are supplemented with iodine, making iodine deficiency rare).

Being female, over 40 years of age, having a close family member with thyroid disease, and recently having had a baby are things that can increase the chance of getting hypothyroidism.

Hyperthyroidism (overactive thyroid). When the thyroid gland is overactive, it makes too much of the thyroid hormone that your body needs to be healthy. This condition affects women more than men. In young women, hyperthyroidism is most often caused by Graves' disease. With this disease, the body's immune system tricks the thyroid into making too much thyroid hormone. The entire thyroid becomes enlarged and overactive. Older women may get another form of hyperthyroidism (toxic nodular goiter), where overactive thyroid cells group together and form a lump in the neck (called a thyroid nodule) that makes more of the thyroid hormone than the body needs. Some thyroid disorders initially cause overactive thyroid, but at a later point in time cause underactive thyroid, due to damage done to the thyroid gland.

Postpartum thyroiditis. After giving birth, a woman's thyroid can swell and become larger or inflamed. This can cause changing levels of thyroid hormone in the body. Sometimes high levels can be followed by low levels of thyroid hormone. After 6 months or less, this condition usually goes away with no permanent damage to the thyroid. While common, thyroid disorders after pregnancy are often hard to detect since some of the symptoms, such as having trouble sleeping, fatigue, depression, or weight change are viewed as normal when a woman has a new baby. The symptoms can also be mild. Usually only short-term treatment is required until the thyroid recovers normal function. Sometimes after pregnancy, a woman can get hypothyroidism (underactive thyroid), which persists and needs long-term treatment with medication.

Thyroid cancer. This type of cancer is most often found as a lump (or nodule) in the thyroid gland. It is not a common type of cancer and most thyroid nodules are benign (not cancer). Other signs of thyroid cancer include swelling in the lymph nodes of the neck and trouble swallowing or breathing. Although anyone can get thyroid cancer, people who as children had head or neck x-ray treatments for tonsillitis or other conditions (from about the 1920s to the 1960s) are more likely to get this cancer. It is treated with surgery, which removes the cancer, sometimes followed by radioactive iodine therapy, which kills the cancer.

What are the signs of a thyroid disorder?
It can be hard to tell if you have a thyroid disorder because these disorders can have signs that are common and often confused with other conditions. If you think you have a thyroid disorder, talk with your health care provider and ask if a blood test for a thyroid disorder is indicated. A simple blood test measures thyroid stimulating hormone, or TSH, to find overactive and underactive thyroid disorders.

Signs of hypothyroidism, or underactive thyroid, include:

Signs of hyperthyroidism, or overactive thyroid, include:

What Causes Thyroid Disease?

How are thyroid disorders treated?

Can You Prevent Thyroid Disease?

Be Careful About Too Much Soy

Drink Bottled Water

When It Comes to Iodine -- Think Moderation

Stop Smoking

Reduce Your Stress

Articles categories

Steroids profiles

The Thyroid Gland