What Is the Function of the Thyroid?
The human thyroid is a small gland with a very big purpose--to regulate the body's metabolism. Weighing less than an ounce, the thyroid gland is located in the front of the neck and is described as having a "butterfly" shape. The two "wings" (lobes) are joined together by a band of tissue known as the isthmus. The thyroid gland affects every tissue in the body that requires increased cellular activity. The ability to lose or gain weight, heart rate, sensitivity to heat and cold, motor coordination and even fertility can be affected when the thyroid does not function properly.
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T3 & T4
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Those with thyroid disorders are familiar with the medical terms "T3" and "T4" and the necessity of ensuring that the thyroid gland produces normal levels of each. The thyroid is solely responsible for the production of these two hormones. Triiodothyronine (T3) and thyroxine (T4) hormones are secreted into the body by the thyroid through the conversion of iodine--again, a task solely delegated to this little gland. After T3 and T4 are released into the bloodstream, they are dispatched to cells that are responsible for controlling metabolism. A thyroid gland that functions normally will produce 80 percent of T4 and 20 percent of T3.
TSH & Thyroid Hormones
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Sometimes, the level of thyroid hormones will drop too low. When this happens, the pituitary gland, a small gland at the base of the brain, releases what is known as TSH (Thyroid Stimulating Hormone) to encourage the thyroid to produce and secrete more hormones. Once the pituitary gland is satisfied that the thyroid had accomplished its mission, it will cease production of TSH. When these two glands work together cooperatively, the right amount of thyroid hormone is present in the body. However, if an individual has an underlying thyroid disorder in which hormones are over- or under-produced, the release of TSH will irritate and exacerbate the gland and may result in a "goiter" (enlarged thyroid).
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Hyperthyroidism
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Hyperthyroidism is caused when too much thyroid hormone is released into the body, thus resulting in a metabolism that is abnormally rapid. While hyperthyroidism has numerous causes, the symptoms that patients suffer from are essentially the same. They typically feel hotter than normal and experience unexplained weight loss, even though their diet and level of activity remain the same (although some patients gain weight as a result of increased appetite). While physical fatigue is common, a patient with hyperthyroidism may experience difficulty falling and staying asleep or have interruptions in the sleep cycle. Motor tremors, muscle fatigue and heart palpitations are also present. Some patients report mood swings and irritability. The presence of a goiter is typical. Because these symptoms occur gradually, hyperthyroidism is often difficult to diagnose in its early stages.
Hypothyroidism
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Hypothyroidism is the result of a thyroid gland that under-produces the requisite amount of T3 and T4. Like hyperthyroidism, hypothyroidism is often difficult to diagnose on first pass, but it is a common condition. Symptoms of hypothyroidism are characteristic of a slow metabolism and include pronounced weight gain, inability to lose weight, hair loss, intolerance to cold, muscle and joint ache, generalized weakness, memory loss, dry and/or pale skin, decreased or absent libido, and excessive sleeping. In fact, some patients with hypothyroidism report falling asleep while sitting at their desk or at a stop light. Hashimoto's Disease, the most common form of hypothyroidism, has an underlying auto-immune component in which the thyroid is attacked by a patient's own immune system. Dr. James Norman of the Norman Parathyroid Clinic estimates than more than five million people in America are affected by hypothyroidism, with as many as 10 percent of women being affected.
Other Thyroid Conditions
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Hormone production can also be impeded by other conditions affecting the thyroid gland, including thyroid nodules, thyroiditis and cancer of the thyroid. These conditions can often result in an over- or under-production of thyroid hormones.
Care and Treatment of the Ailing Thyroid
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Hyperthyroidism and hypothyroidism are not life-threatening if treated in a timely and appropriate manner. In most cases, hypothyroidism is successfully treated with hormone replacement medication, such as Synthroid. Hyperthyroidism is a bit trickier to treat and includes use of oral medications that inhibit thyroid production. Additionally, a beta blocker is used to decrease symptoms such as increased heart rate and excessive sweating. If a patient's symptoms are severe or return after treatment, sometimes a physician will recommend radioactive iodine treatment to "kill" a portion the thyroid. However, many times this treatment results in the destruction of all thyroid cells, and patients become severely hypothyroidic. In some cases, thyroid replacement therapy yields little success for these patients. It is always advised that patients considering this treatment consult with their physician about the long-term effects of radioactive iodine treatment.
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