Tyrosine: Precursor of Thyroid Hormones

by Kevin Ahern, PhD

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    Now, tyrosine is also a precursor of the thyroid hormones. And this is an interesting set of reactions that occur in the cells of our thyroid gland. I'm going to step you through the process and we'll see what happens here. So thyroglobulin is a protein that's necessary for making the thyroid hormones. It literally provides a substrate on which the individual thyroid hormones are synthesized as we can see here. Thyroglobulin synthesis begins in the endoplasmic reticulum. And after it has been made, it is excreted out of the endoplasmic reticulum out of the cell into the extracellular space. And that's the process you see with those pink arrows moving to the left. Thyroglobulins serve as a substrate because sticking off of it are the precursors of what will become the thyroid hormones. Those are those little hexagonal structures that you can see by the secreted protein on the left. The export from the cell, as I said, releases the thyroglobulin out into the extracellular space. So, the synthesis of thyroid hormone is not occurring inside of a cell, it's actually outside the cell where this process occurs. Critical for making the thyroid hormones is the ion iodide. So, iodide is important for the synthesis for the thyroid hormones. Iodide is found in the bloodstream and has to be moved out of the bloodstream into the cell and then ultimately into that extracellular space where it can be joined with the precursors on the thyroglobulin. We see that process happening in this set of reactions. That is first of all the iodide in the blood is grabbed by the sodium-iodide symporter which moves both ions into the cell. We see that happening. After iodide has gotten into the cell, it's then transported out of the cell by another transporter...

    About the Lecture

    The lecture Tyrosine: Precursor of Thyroid Hormones by Kevin Ahern, PhD is from the course Amino Acid Metabolism. It contains the following chapters:

    • Tyrosine is a Precursor of Thyroid Hormones
    • Tyrosine Metabolism

    Included Quiz Questions

    1. The include thyroxine and triiodothyronine.
    2. They are made inside of thyroid cells.
    3. They are made from a precursor derived from tyrosine called thyroglobulin.
    4. All of the answers are correct.
    5. None of the answers are correct.
    1. All of the answers are true.
    2. All deiodinases contain selenium.
    3. Triiodothyronine, with three iodines, is the most active form.
    4. Iodide ion is imported into thyroid cells from the bloodstream.
    5. None of the answers are true.
    1. All of the answers are true.
    2. It is a factor in phenylketonuria.
    3. It is treated by reducing intake of phenylalanine and tyrosine.
    4. It can result in black urine disease.
    5. None of the answers are correct.

    Author of lecture Tyrosine: Precursor of Thyroid Hormones

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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