T3 And T4 Tests: A Closer Look

A thyroid function test is used to check the function of the thyroid gland. It is a blood test used to detect hyperthyroidism or hypothyroidism. The T3 test checks for levels of the hormone triiodothyronine, and the T4 test measures the blood level of the hormone T4, also known as thyroxine. Before we delve into the test itself, let’s talk about what these hormones are.

Triiodothyronine (T3) and thyroxine (T4) are hormones released by our thyroid gland — a butterfly-shaped gland sitting low on the front part of our neck. The two hormones help our body’s physical and brain development and metabolism. Both hormones help the muscles, the heart, the liver, and the brain to function well.  For our body to produce these two hormones, TSH or Thyroid Stimulating Hormone must be produced. TSH is produced by the anterior pituitary gland, a small, pea-sized gland located at the base of our brain. 

The thyroid works by taking iodine found in our diet, combining it with an amino acid called tyrosine, then converting it into T4 and T3. The T4 contains four atoms of iodine, and the T3 has three iodine atoms. The T4 hormone is inactive. It is a storage hormone that works to transport T3 throughout our body. T4 must be converted to T3 before our body can actively use it.

Twenty percent of our body’s T3 is delivered into the bloodstream by the thyroid gland. The other 80 percent is made by our liver or kidneys in a process called deiodination. Thyroid function tests are designed to detect hyperthyroidism and hypothyroidism. 

 According to the American Thyroid Association, there isn’t one test for every situation as there are several kinds of thyroid tests. But your doctor may provide an initial TSH level blood test. This is because the TSH level can serve as an indication of more specific issues.

Signs and symptoms such as chronic constipation, weight gain, memory issues, and fatigue could indicate hypothyroidism. Thyroid testing is also frequently requested by psychiatrists to rule out thyroid abnormalities in psychiatric patients. Hypothyroidism mimics a depressive episode with similar symptoms of fatigue, anhedonia, weight gain, and sleep disturbance. 

In contrast, hyperthyroidism could cause palpitations, weight loss, nervousness, anxiety, and irritability. These symptoms are usually also present in anxiety disorders. High T3 levels are most commonly caused by thyroid disorders like Graves’ disease, goiter, and thyroid tumors. Health risks of high T3 include pregnancy complications, high cholesterol, liver disease, and sexual dysfunction.

A regular T3 and T4 health check is needed to know and identify early signs of health issues. T3 and T4 travel together in our bloodstream to reach almost every cell in the body. They regulate how fast our body uses energy. For instance, both control our weight, body temperature, and heart rate. Regular health checks are also encouraged among elders because diagnoses can be difficult since hypothyroidism signs and symptoms are attributed to aging.

Are there ways to support our thyroid health? The best thing to do is lifestyle modification. Manage your stress through yoga, meditation, expression of creativity, and regular reconnection with nature. Eat well and choose whole foods rather than processed ones. And do not forgo exercise and movement. Don’t forget — that little regular walk in the park can trim your waistline.