Free T3 refers to the free or unbound form of triiodothyronine, which is a thyroid hormone. Triiodothyronine (T3) is one of the two main thyroid hormones produced by the thyroid gland, with the other being thyroxine (T4). While T4 is the most abundant thyroid hormone, T3 is considered the more biologically active form.
When the thyroid gland produces T4, a portion of it gets converted into T3 in various tissues throughout the body. T3 plays a vital role in regulating metabolism, growth, development, and other essential bodily functions. It influences the rate at which cells produce energy, affects body temperature, and impacts the functioning of organs and tissues.
The term "free T3" refers to the unbound or unattached T3 hormone circulating in the bloodstream. It is called "free" because it is not bound to proteins that transport thyroid hormones in the blood. Free T3 is the form of T3 that can readily enter cells and exert its effects.
Measuring free T3 levels can provide valuable information about thyroid function and metabolism. It helps assess if an individual's body is receiving an adequate supply of active thyroid hormone. Abnormal levels of free T3, either too high or too low, can indicate an imbalance in thyroid function and may be associated with various thyroid disorders, such as hyperthyroidism or hypothyroidism.