Triiodothyronine (T3)

Definition

Triiodothyronine (T3) is a thyroid hormone that plays crucial roles in metabolism, growth, and development. It is more potent than thyroxine (T4) and exerts significant effects on nearly every physiological process in the body.

5 Must Know Facts For Your Next Test

1. T3 is produced by the thyroid gland and also by the conversion of T4 to T3 in peripheral tissues.
2. T3 has a higher affinity for thyroid hormone receptors compared to T4, making it more biologically active.
3. In pharmacology, synthetic T3 is known as liothyronine and is used to treat hypothyroidism.
4. Abnormal levels of T3 can indicate various thyroid disorders such as hyperthyroidism or hypothyroidism.
5. The half-life of T3 in the bloodstream is approximately one day, which is shorter than that of T4.

Review Questions

• What are the primary roles of triiodothyronine (T3) in the body?
• How does T3 compare to T4 in terms of biological activity?
• What synthetic form of T3 is commonly used in treating hypothyroidism?

Related terms

Thyroxine (T4): A thyroid hormone that converts into the more active form, triiodothyronine (T3).

Hypothyroidism: A condition characterized by insufficient production of thyroid hormones.

Hyperthyroidism: A condition where there is excessive production of thyroid hormones.