Difference between T3 and T4 in thyroid gland

Answer 1

T3 and T4 are both hormones produced by the thyroid gland, but they differ in terms of their structure and function.

- Structure: T3, also known as triiodothyronine, is a hormone made up of three iodine atoms, while T4, also known as thyroxine, is a hormone made up of four iodine atoms. This structural difference accounts for some of their differences in function.

- Function: T3 is considered the more biologically active form of thyroid hormone. It has a stronger binding affinity to thyroid hormone receptors and is more potent in terms of its effects on metabolism and other bodily processes. T4, on the other hand, is considered a prohormone that gets converted into T3 within cells. It is the main form of thyroid hormone produced by the thyroid gland and is responsible for maintaining a steady level of thyroid hormones in the blood.

- Conversion: T4 is converted into T3 primarily in the liver and other tissues. This conversion is catalyzed by enzymes called deiodinases. The conversion is important because T3 is the hormone that interacts with thyroid hormone receptors and exerts its effects on various tissues and organs.

- Duration of action: T4 has a longer half-life in the blood compared to T3. This means that T4 remains in circulation for a longer duration and has a more sustained effect on target tissues. T3, on the other hand, has a shorter half-life and is more rapidly metabolized or cleared from the blood.

Overall, T4 serves as the precursor for T3 and helps to maintain a continuous supply of thyroid hormone in the body. T3, being the more active form, exerts its effects on cellular metabolism and regulates various physiological processes. Both hormones are important for maintaining proper thyroid function and overall health.