Free T3 and Free T4 Blood Test Panel
The Free T3 and Free T4 Blood Test Panel evaluate thyroid function if a thyroid disorder is suspected.
What is a thyroid?
The thyroid is a gland in the neck, above the collarbone, shaped like a butterfly. The thyroid is one of the endocrine glands which produce hormones. These thyroid hormones help regulate the rate of many activities in the body, such as how fast calories are burned and how fast the heart beats.
What is the purpose of this test?
Order this Free T3 and Free T4 Blood Test Panel to evaluate thyroid function if a thyroid disorder is suspected. In addition, individuals may use this panel to evaluate pituitary gland function, assess the severity of thyroid disorder, monitor treatment, and detect potential side effects.
This panel includes the following:
Free T3 - normally represents only approximately 5% of the thyroid hormone. Like thyroxine, it is almost entirely bound to the carrier proteins, with only 0.25% of the total being free. Measurement of Free T-3 is of value in confirming the diagnosis of hyperthyroidism when an elevated free or total thyroxine level is found. Abnormal total and free tri-iodothyronine concentrations can appear in T3 toxicosis in normal thyroxine levels. Free T3 levels are not affected by carrier protein variation.
Free T4 - is the active form of thyroxine and is a more accurate reflection of thyroid hormone function. The free T4 test is thought to be a more accurate reflection of thyroid hormone function, and, in most cases, its use has replaced that of the total T4 test. A total T4 or free T4 test is primarily ordered in response to an abnormal TSH result. However, sometimes the T4 will be ordered along with a TSH to give the doctor a complete evaluation of the adequacy of the thyroid hormone feedback system. These tests are usually ordered when a person has symptoms of hyperthyroidism or hypothyroidism.
When should I order the Free T3 and Free T4 Blood Test Panel?
Individuals may order this panel if they suspect a thyroid disorder. Common signs or symptoms associated with thyroid malfunction or disorders include:
- Weight loss or gain
- Painful joints and muscles
- Dry skin
- Thin/dry hair
- Irregular heart rate
- Depression and anxiety
- Mood swings
- Irregular menstrual periods
- Frequent bowel movements
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