How Does Thyroid T3 Supplement Work?

The thyroid gland is a small gland located in the front of your windpipe. It releases hormones that control your metabolism, which is your body's ability to burn calories. T3, or triiodothyronine, is one type of thyroid hormone released from the thyroid gland. If your thyroid gland does not secrete enough of this hormone, you may need a T3 supplement prescription.

The Thyroid

Lab Tests Online, a website from the American Association for Clinical Chemistry, explains that an area of the brain called the hypothalamus creates thyrotropin-releasing hormone, or TRH, when levels of thyroid hormone in the blood become low. This stimulates the creation of thyroid-stimulating hormone, or TSH, from a gland below the brain called the pituitary gland. This, in turn, stimulates the thyroid gland to create and release thyroid hormone. The thyroid produces two types of hormones: thyroxine, or T4, and T3. The thyroid gland produces mostly T4, which is considered the inactive form of thyroid hormone. T3 is considered the active form of thyroid hormone that the body uses. T4 is converted to T3 in tissues such as the liver.

How T3 Works

According to "Mosby's Manual of Diagnostic and Laboratory Tests," T3 only makes up 7 to 10 percent of total thyroid hormone. In addition, 70 percent of T3 is bound to proteins called thyroxine-binding globulin and albumin. The rest of T3 is unbound or free, which is considered the active form. The levels of T3 and T4 are regulated by a feedback loop. Therefore, high levels of T3 and T4 suppress the release of TRH, leading to a suppression of TSH and consequently a suppression of thyroid hormone. On the other hand, low levels of T3 and T4 stimulate the release of TRH, which then stimulates the release of TSH, which then stimulates the release of thyroid hormone.

T3 Supplements

T3 supplements are known by the generic name liothyronine and by the brand names Cytomel and Triostat. T3 supplements increase the basal metabolic rate, stimulate the body's utilization of oxygen and promote the breaking down of proteins, carbohydrates and fats. Liothyronine is absorbed into the tissues rapidly because it is not tightly bound to proteins. In fact, 95 percent of T3 is absorbed within four hours, notes Daily Med, a website from the U.S. National Library of Medicine.

Indications For Use

According to Daily Med, liothyronine is used as a supplement or thyroid hormone replacement for people with hypothyroidism, which is a condition characterized by low levels of thyroid hormone in the body. Other approved uses for liothyrornine include suppression of the release of TSH from the pituitary gland, prevention or treatment of euthyroid goiters and thyroid suppression tests to diagnose thyroid gland autonomy or mild hyperthyroidism.


Daily Med notes those recovering from a type of hypothyroidism known as subacute thyroiditis should not use liothyronine. It is also contraindicated in those with thyrotoxicosis that has not been treated, adrenal cortical insufficiency and allergy to any of its ingredients. According to the PubMed Health website, possible side effects of liothyronine include nausea, vomiting, diarrhea, stomach cramps, weight loss, increased appetite, headache, tremor, nervousness, insomnia, irritability, sweating, fever, increased sensitivity to heat, menstrual cycle changes and hair loss.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.
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