Podcast
Questions and Answers
What is a primary function of T3?
What is a primary function of T3?
Which protein does NOT primarily bind thyroid hormones in circulation?
Which protein does NOT primarily bind thyroid hormones in circulation?
Which statement about the plasma concentration of T4 and T3 is true?
Which statement about the plasma concentration of T4 and T3 is true?
How are T4 and T3 primarily excreted?
How are T4 and T3 primarily excreted?
Signup and view all the answers
Why is the biologic activity mainly attributed to T3?
Why is the biologic activity mainly attributed to T3?
Signup and view all the answers
What role does T3 play in human growth and development?
What role does T3 play in human growth and development?
Signup and view all the answers
Study Notes
Biological Function of T4 and T3
- T4 and T3 act on nearly every cell in the body.
- T3 increases the rate of metabolism and oxygen consumption in all body tissues except brain, gonads, and reticuloendothelial system (RES).
- T3 increases the activity of Na+/K+ pump in all body tissues.
- T3 has an anabolic effect.
- T3, along with GH, regulates long bone growth and neural maturation.
- T3 is essential for proper development and differentiation of all human cells.
- T3 plays a role in human heat generation.
Transport of T4 and T3
- Nearly all thyroid hormones in the circulation are protein-bound, while the remaining small-unbound (free) fraction is responsible for biological activity.
- Thyroid hormones are primarily bound to thyroxine-binding globulin (TBG) and to a lesser extent to thyroxine-binding prealbumin and albumin.
- TBG binds T4 with greater affinity than T3.
- The plasma half-life of T4 is higher than that of T3, resulting in a higher plasma concentration of total T4.
- The free fraction of T3 (0.2% of plasma T3) is higher than that of T4 (0.05% of plasma T4).
- The plasma concentration of free T3 is nearly equal to that of free T4, making T3 the primary contributor to biological activity.
Metabolism of T4 and T3
- T4 and T3 are metabolized in the liver.
- They are conjugated with glucuronate or sulphate to be excreted in urine and, to a lesser extent, in feces.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz covers the functions of T4 and T3 hormones, including their effects on metabolism, oxygen consumption, and cell growth.
