General Health

Components of Thyroid Hormone Profile Test


Triiodothyronine is a thyroid hormone that regulates metabolism and maintains that your body can fulfil its necessary functions. While the majority of T3 in the bloodstream is linked to protein, some is not linked known as bioavailable T3 or free T3. The active form of T3 that is not bound to protein is measured in the free T3 test. The total T3 test combines bound and free T3 measurements.

If a thyroid disorder is suspected, blood tests for free T3 or total T3 may be done to assess thyroid function. They can also be used to diagnose pituitary gland disorders, determine the severity and type of thyroid disease, and review the effectiveness of thyroid medication.

Thyroid function is evaluated using both free T3 and total T3 assays. Free and total T3 testing, along with other thyroid function tests, are used to diagnose thyroid abnormalities such as a hyperactive or hypoactive thyroid gland, as well as to assess the severity of thyroid problems, diagnose pituitary gland disorders, and monitor patients with known thyroid conditions.

If an individual has had an abnormal thyroid-stimulating hormone (TSH) test, T3 testing might be employed as a part of further testing.

Thyroid function can be assessed using either of the following tests:

  • Thyroid replacement therapy effectiveness can be determined via free T3 testing. It can also aid in the diagnosis of thyroid hormone-binding protein disorders.
  • Many studies suggest that total T3 is a more appropriate measurement than free T3. Total T3 can be used to identify hyperthyroidism or a pituitary gland disease, as well as to determine the origin of an overactive thyroid and track a patient’s response to hyperthyroidism treatment.


The severity of the hormone imbalance affects the signs and symptoms of thyroid problems. Problems usually emerge gradually, over a period of several years.

  • Cachexia involves marked weight loss and muscle loss
  • Feeling overtired, all the time with low energy and a strong desire to sleep that interferes with normal daily activities
  • Frequent bowel movements
  • Hair loss (alopecia) can affect your entire body or simply the scalp
  • Increased appetite
  • Sweating might become considerable
  • Menstruation can become inconsistent
  • Palpitations in the heart
  • Insomnia
  • Anxiety or nervousness
  • Concentration difficulties

T3, whereas useful in some cases, is less useful in diagnosing hypothyroidism because it is the last hormone to become abnormal in hypothyroid patients.

Normal values

Free T3 or total T3 test assess T3 is within the normal range, below normal, or above normal.

From one laboratory to the other, the reference ranges may differ slightly. Below are the following reference ranges:

  • Free T3 2.3–4.2 picograms per millilitre (pg/mL)
  • Total T3 80–180 nanograms per deciliter (ng/dL)

Elevated T3 levels

T3 levels that are abnormally high may indicate a thyroid disease such as Basedow’s disease,

  • Hyperthyroidism
  • Thyroiditis
  • Periodic thyrotoxic paralysis

Low T3 levels

T3 levels that are too low could indicate hypothyroidism or malnutrition. Because T3 levels decrease when an individual is sick, it could also signify that the patient has a long-term disease.

This is one of the grounds why health care professionals don’t utilise the T3 test as a thyroid test on a regular basis. Instead, they frequently combine it with the T4 and TSH tests to obtain a more overall understanding of your thyroid’s activities.


T3, also known as triiodothyronine, is a thyroid hormone with numerous functions in the body. T3 regulates the body’s metabolism, activates cells, and allows key organs to function alongside thyroxine, another important thyroid hormone.

T3 refers to the hormone triiodothyronine, which has three iodine atoms connected to it. Thyroxine (T4), the other primary thyroid hormone, has four iodine atoms. The thyroid produces some of the T3 that circulates in your body. The majority of it, on the other hand, begins as T4 and is changed to T3 in the blood by the removal of one iodine atom.

As it circulates in the bloodstream, more than 99 percent of T3 in the body is bound to proteins. Free T3 refers to the fraction of T3 that is not linked to proteins. Only free or bioavailable T3 has the ability to interact with cells and activate a variety of physical processes. The body regulates the interaction between bound and free T3 in a very precise balance to guarantee optimal physiological functions.

The total T3 test counts both bound and free T3, whereas the free T3 test only counts T3 that isn’t bound to protein.

T3 levels are frequently used in conjunction with other thyroid function tests, such as TSH and free and total T4, to assess how well your thyroid is working.


 Yash Batra

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