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Thyroid Function Test Level I

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The combination of the Thyroid Profile (T3T4T7) and the Thyroid Stimulating Hormone (TSH) test is ideal for evaluating thyroid function and/or symptoms of an overactive thyroid (hyperthyroidism) or an underactive thyroid gland (hypothyroidism). The thyroid is the master gland that regulates the body's metabolism and is responsible for the process of caloric burning and energy conservation. The thyroid sits at the base of the neck and is often described as a bow-tie shaped gland.

The Role of the Thyroid

According to the Center for Disease Control and prevention, thyroid dysfunction is especially common in older people and women, affecting over 30 million people in the U.S. If you have been experiencing unexplained weight gain, mood changes, fatigue or sudden weight loss, you may benefit from thyroid testing. These blood tests measure the levels of the hormones that influence the function of the thyroid, and may indicate a hormonal imbalance is the cause of changes in your metabolism. As a result, the thyroid may be overactive (hyperthyroidism) or underactive (hypothyroidism).

The Thyroid Level I Test Evaluates Normal Function

A healthy functioning thyroid needs a balanced level of thyroid stimulating hormone or TSH, T3, and T4. Together these hormones stimulate the gland and store hormones that increase or decrease energy expenditure. The thyroid is also related to the role of other body systems and may cause certain symptoms if it is not functioning at optimum. The role of these hormones may include:
  • The thyroid stimulating hormone or TSH signals the thyroid to perform its job and burn calories.
  • T3 is the active thyroid hormone that informs the body cells to use digested food as energy and to not store it as fat.
  • T4 circulates in the blood and influences how other organs and the heart function in the body.
  • T7 is a calculated measure of T4 x T3U (T3 Uptake)

High Levels of TSH and Low Levels of Thyroid Hormones

If the TSH level is high, it may mean this hormone is trying hard to signal the thyroid to function normally. The T3 and T4 test may reveal these blood concentrations are at insufficient levels. These values may be indicative of an underactive thyroid and people may experience signs and symptoms such as:
  • Unexplained weight gain
  • Tiredness that is unrelieved by rest or sleep
  • Depression
  • Muscle weakness or joint pain
  • Constipation
  • Increased sensitivity to cold
  • Pale dry skin
  • Swelling around the face
  • Voice changes or hoarseness

Low Levels of TSH and High Levels of Thyroid Hormones

Conversely, excessive concentrations of hormones may cause over-stimulation of the body and cause hyperthyroidism or an overactive thyroid. The low levels of TSH and high concentrations of T3 and T4 may indicate thyroid dysfunction. Signs and symptoms of an overactive thyroid may include:
  • Rapid heartbeat and excessive sweating
  • Unexplained weight loss
  • Anxiety and wide mood swings
  • Insomnia and hyperactivity
  • Shaking hands and tremors
  • Heat intolerance and itching
  • Muscle weakness
  • Swelling of the neck area

When Should Men and Women have a Thyroid Test?

The American Thyroid Association recommends that all adults be tested beginning at age 35 and be tested every five years thereafter. In addition, people with family members that have experienced thyroid dysfunction may want to be tested sooner and more often. The American Thyroid Association also recommends those who experience signs or symptoms of thyroid abnormalities to be tested.

Treatment for an Imbalanced Thyroid

Treatment involves restoring the healthy functioning of the thyroid (hormone replacement therapy or HRT) as prescribed by a physician. The prognosis is usually good and most people enjoy a much better quality of life as their energy and brighter mood return to normal. People also report experiencing an improved restful sleep, younger and smoother skin and a return to a normal weight.

Additional Lab Tests for Abnormal Thyroid Diagnoses

The thyroid is a delicate gland that is susceptible to environmental chemicals, certain medications and stress. Recent studies have provided evidence that cortisol and adrenal insufficiency may impact the thyroid in a negative manner. Women and men over 50 may be particularly affected due to the changes of hormones in the body. It is recommended for the over-50 age group that an adrenal and cortisol test also be administered when evaluating the thyroid for dysfunction.