Dr. Saoji Orthopaedic Clinic And Medilab Pathology Laboratory
Sky Orthopaedics,1st Floor, Nikalas Tower, Central Bazar Road,Nagpur
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Know About Free Triiodothyronine (FT3)
Triiodothyronine (T3) is one of two major hormones produced by the thyroid gland, a small butterfly-shaped organ that lies flat across the windpipe at the base of the throat. The other major thyroid hormone is called thyroxine (T4) and together they help control the rate at which the body uses energy. Almost all of the T3 (and T4) found in the blood is bound to protein. The rest is free (unbound) and is the biologically active form of the hormone. Tests can measure the amount of free T3 or the total T3 (bound plus unbound) in the blood.
Pituitary-Thyroid Feedback System
T3 and T4 production is regulated by a feedback system. When blood levels of thyroid hormones decline, the hypothalamus releases thyrotropin releasing hormone, which stimulates the pituitary gland to produce and release thyroid-stimulating hormone (TSH). TSH then stimulates the thyroid gland to produce and/or release more thyroid hormones. Most of the thyroid hormone produced is T4. This hormone is relatively inactive, but it is converted into the much more active T3 in the liver and other tissues.
If the thyroid gland produces excessive amounts of T4 and T3, then the person affected may have symptoms associated with hyperthyroidism, such as nervousness, tremors of the hands, weight loss, insomnia, and puffiness around dry, irritated eyes. In some cases, the person's eyes cannot move normally and they may appear to be staring. In other cases, the eyes may appear to bulge.
If the thyroid gland produces insufficient amounts of thyroid hormones, then the person may have signs and symptoms associated with hypothyroidism and a slowed metabolism, such as weight gain, dry skin, fatigue, and constipation. The blood levels of thyroid hormones may be low or high due to thyroid dysfunction or rarely due to insufficient or excessive TSH production related to a pituitary disorder.
The most common causes of thyroid dysfunction are related to autoimmune disorders. Graves disease causes hyperthyroidism, but it can also be caused by thyroiditis, thyroid cancer, and excessive production of TSH. The effect of these conditions on thyroid hormone production can be detected and monitored by measuring the free T3 or sometimes total T3.
FT3; Free Triiodothyronine.
To help evaluate thyroid gland function; to diagnose thyroid disease, including hyperthyroidism, and determine the cause; to monitor effectiveness of treatment of a thyroid disorder. When you have an abnormal TSH, particularly with a normal free T4 result, and/or signs and symptoms of hyperthyroidism.
A free T3 or total T3 test may be ordered when someone has an abnormal TSH test result. It may be ordered as part of the investigative workup when a person has symptoms suggesting hyperthyroidism, especially if the free T4 level is not elevated.
Signs and symptoms may include:
Increased heart rate
Tremors in the hands
Light sensitivity, visual disturbances
The eyes may be affected: puffiness around the eyes, dryness, irritation, and, in some cases, bulging of the eyes.
Free or total T3 may sometimes be ordered at intervals to monitor a known thyroid condition and to help monitor the effectiveness of treatment for hyperthyroidism.