T3 Test 101: The basics

Introducing T3 test

Every human has a thyroid gland. This small, but very useful gland is located in the neck. It lies just below the Adam’s apple. They thyroid gland, like every other gland, produces hormones and regulates the body’s usage of energy. It also regulates the body’s sensitivity to other hormones.

One hormone produced by the thyroid gland is triiodothyronine. This hormone is known informally as T3. The thyroid gland also produces thyroxine, another hormone. This is known as T4. These hormones work together to regulate heart rate, metabolism, temperature, and other essential functions.

T3 binds readily to proteins in the body. Some T3, however, does not bind to proteins – these are known as free T3. Free T3 circulates freely in the blood. The blood levels of both forms of T3 is determined by a test known as the T3 total test. The T3 test allows your doctor to determine whether you have a thyroid disorder or not.

T3 test
Photo Credit: Blood Tests in London

What is the significance of a T3 test?

Most doctors call for a T3 test when they suspect that the patient has a thyroid problem.

Examples of thyroid problems include:

  • Hyperthyroidism: This is a condition characterized by the excessive production of thyroid hormone.
  • Hypopituitarism: In this condition, the thyroid gland fails to produce an adequate amount of pituitary hormones
  • Primary or secondary hypothyroidism: Here, there is inadequate production of thyroid hormones.
  • Thyrotoxic periodic paralysis: This is characterized by excessive production of thyroid hormones resulting in muscle weakness.

Thyroid disorders are accompanied by many symptoms. The patient may experience mental issues like anxiety. He or she may also experience physical symptoms like menstrual irregularity or constipation.

Other symptoms that accompany a thyroid disorder include:

  • Fatigue and weakness
  • Insomnia
  • Increased sensitivity to temperature
  • Excessive gain or loss of weight
  • Puffy or dry skin
  • The eyes become irritated, bulging, or puffy
  • Hair loss
  • Tachycardia or increased heart rate
  • Hand tremors

If you’ve been diagnosed with a thyroid problem, your doctor may call for a T3 test to know whether your condition has undergone some changes or not. In some cases, he or she may call for a TSH test or a T4 test. TSH is an acronym for thyroid stimulating hormone. TSH stimulates the thyroid gland to produce the real thyroid hormones – T3 and T4. By knowing the level of each of these hormones, your doctor can determine with accuracy what exactly is wrong with your gland.

What do I need to do before going for a T3 test?

If you are currently on medications, then you should inform your doctor. Some medications can affect the result of a T3 test. If your doctor is well-informed of the medications, he or she may ask you to stop taking them briefly, and then continue after the test.

Examples of medications that may have effects on T3 levels include:

  • Steroids
  • Thyroid medications
  • Birth control pills or medications that contain hormones (estrogens and androgens).

What is the procedure for a T3 test?

Basically, the patient’s blood will be drawn and then sent to the laboratory for analysis.

The normal results for a T3 test are between 100 to 200ng/dL. That a person has a normal T3 test result does not mean that his or her thyroid gland is in perfect working condition. With a T3 and T4 test, your doctor will be able to determine whether you have a thyroid problem or not.

Interpreting abnormal T3 test results

The physiology of the thyroid gland is quite complicated. Because of this, your doctor may be unable to determine what exactly is wrong with a single test result. However, with an abnormal result, the doctor may be able to figure out what exactly is wrong. He or she may order for a T4 test or a TSH test to get a better picture of your thyroid function.

Pregnant women usually have very high levels of T3. The same applies to individuals with liver disease. If your doctor goes further to determine the T3 level, then he or she may be able write off these conditions.

High T3 levels

If an individual doesn’t have a liver disease, or is not pregnant but has a high T3 level, then it may be an indication of conditions such as:

  • Hyperthyroidism
  • Grave’s disease
  • Thyrotoxic periodic paralysis
  • Silent thyroiditis
  • Toxic nodular goiter

Elevated T3 levels may also be an indication of excessive protein in the blood. Sometimes, it may also be due to thyrotoxicosis or thyroid cancer.

Low T3 levels

When the T3 levels are extremely low, then it may be an indication of starvation or hypothyroidism. It could also mean that the individual has a chronic health disorder as T3 levels fall drastically when a person is sick. This explains why most physicians do not use T3 test as routine. Instead, they may use T3 plus TSH and T4 test to get a more comprehensive view of the thyroid function.

Does the T3 test have any risks?

Some people may experience slight discomfort when blood is being drawn. The patient may also have very slight bleeding. Sometimes, there may be lightheadedness.

Serious symptoms include infection, fainting, inflammation of the vein, and bleeding.

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