Triiodothyronine: T3 And T3 Tests

Feature | Triiodothyronine: Everything You Need To Know About T3 and T3 Tests | t3
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What is triiodothyronine? What is its significance in thyroid health? We talk about it and T3 tests below.
RELATED: Understanding TSH Levels: Important For Your Thyroid Function
In this article:

  1. What T3 and T4 Are
  2. What a Triiodothyronine or T3 Test Measures
  3. Types of T3
  4. What T3 Tests Involve
  5. Dealing with Low T3

Triiodothyronine and T3 Tests: Things You Must Know

When a doctor orders a “T3 test,” it’s not unusual for the patient to be unfamiliar with the term. The name of this test refers to the level of triiodothyronine in the patient’s system.
Whether T3 levels are found to be high, low, or normal determines how any problem the patient is experiencing might be treated.

What are T3 and T4?

The thyroid gland produces two hormones, both of which are important to the body. They are known as triiodothyronine T3 and thyroxine T4.
Another hormone also comes into play when it comes to thyroid function. It’s known as TSH, and it regulates how much T3 and T4 the thyroid produces.
TSH is produced by the pituitary gland. If a patient seems to be having a thyroid-related issue, a doctor may order a blood thyroid test measuring TSH, as well as T3 and T4 levels.
T3 and T4 hormones each play an important part in maintaining one’s health. They regulate heart rate, temperature, and metabolism. T4 often acts as a “storage hormone,” eventually converting to T3 for energy.
Abnormal levels of either one may lead to hypothyroidism (from low thyroid hormone production) or hyperthyroidism (from high thyroid hormone production). These can lead to problems ranging from weight changes, vision problems, fatigue, racing heart, anxiety, and constipation.
At their worst, thyroid cancer can occur.

What Does a Triiodothyronine or T3 Test Measure?

blood sample thyroid hormone t3 result | Triiodothyronine: Everything You Need To Know About T3 and T3 Tests | normal tsh levels
The T3 test determines how much T3 is in a patient’s system. If the triiodothyronine function appears to be normal, the doctor may also order tests to see if normal TSH levels and T4 levels are present.
A normal T3 level is between 100 to 200 nanograms per deciliter.
T3 Test Results:
If T3 is lower than normal, hypothyroidism may be the problem. Normal TSH levels and low T3 tend to point to hypothyroidism, which is rarer than hyperthyroidism — and less understood.
Weight gain, extreme fatigue, a slower heart rate, constipation, dry skin, and thinning hair are among the potential symptoms. Some people even develop an enlarged neck, known as a goiter.
But low T3 can also indicate malnutrition or other illnesses. For that reason, a result of low T3 will not be automatically attributed to hypothyroidism.
A doctor is likely to order additional tests to determine the underlying cause of the triiodothyronine (T3) levels.
If T3 is higher than normal, a number of thyroid issues may be the cause. These include hyperthyroidism, Grave’s disease, and thyrotoxic periodic paralysis.
Many symptoms of hyperthyroidism are almost the exact opposite of those of hypothyroidism. They include weight loss, nervousness, faster heart rate, more frequent bowel movements, and excessive sweating.
While it’s not common, high T3 can also point to the presence of thyroid cancer.

What are the Types of T3?

Once T3 is produced, it behaves in two ways.
Most of it binds to proteins in the bloodstream. The other kind, known as free triiodothyronine, or free T3, does not bind to proteins.
A “total T3” test measures the presence of both types of T3.
It’s also important that T4 be able to convert to T3 when needed.
For some patients, this conversion isn’t as efficient as it should be. That leads to lower amounts of available T3. Hypothyroidism is a common outcome of abnormally low amounts of T3 and may go undetected if a test indicating a TSH normal range is all the physician has to go on.
Some root causes of hypothyroidism include radiation treatment, thyroid surgery, autoimmune disorders, and complications from medications. Iodine deficiency, though less common in the U.S., may also be a factor.
RELATED: 13 Ashwagandha Benefits For Your Thyroid Health
If the body is converting T4 into “reverse T3” instead of regular T3, the body can go into a kind of shutdown mode, in which systems work much slower than normal. That’s when a person may experience symptoms such as fatigue, slowed heart rate, and weight gain.

What Do T3 Tests Involve?

The test that measures triiodothyronine function is a relatively simple one. The patient just needs to have blood drawn, which the laboratory then tests.
If the results don’t appear to show the entire picture, the doctor may order a complete set of tests, which will also measure T4 and TSH levels.
The tests cause only minor discomfort for most patients. As with any blood draw, however, be prepared for feeling light-headed and to experience minor bruising.
Less often, patients may faint or bleed excessively, but that is rare. Follow the physician’s advice about whether or not fasting or restricting medication is necessary prior to the test.

Dealing with Low T3

Many patients are prescribed a synthetic hormone to help regulate hormone levels. This treatment works for many people to decrease symptoms like fatigue and weight gain.
What else can be done to encourage the body to convert T4 into T3?
In addition to other treatments, ask a doctor about thyroid support supplements. Specifically, choose a product that addresses complaints related to an underactive thyroid, and encourages conversion of T4 to T3.
In addition, a supplement should contain ingredients that support healthy thyroid function in general. Extra iodine can be beneficial, in case the patient has problems absorbing it from diet alone.
Other nutrients, such as selenium and vitamin K2, are helpful for thyroid function and for the healthy circulation needed to deliver proper T3 levels.
Herbal ingredients have also been found to be beneficial in treating underactive thyroid issues. Guggulsterone, from the Guggul tree, boosts thyroid function.
Olive leaf extract supports healthy metabolism and increased energy. Theobromine, a compound found in the cocoa plant, is a mood elevator.
Learn how high your T3 should be in this video from Dr. Alan Christianson:

An abnormal thyroid test does not have to be devastating news. There are a number of prescription drugs and even surgical options that can correct more serious problems.
For many, making dietary changes and taking supplements can make a key difference, or support more aggressive treatment. Discuss all of these options with a reputable doctor.
How do you manage low T3 levels? Do you take supplements? Let’s talk about thyroid health in the comments below.
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