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Euthyroid Hyperthyroxinemia – Euthyroid Conditions

by Carlo Raj, MD
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    A topic that you want to be extremely comfortable with is called euthyroid conditions in laboratory investigation. As simple as this may seem, there are certain things that you want to take at a dissection that is going to help you differentiate one type of thyroid pathology from the another. Do not underestimate what I have to tell you now. This brings us to our first discussion of euthyroid. Break it up. Eu- prefix – normal. Thyroid. A pathology is going to lie within hyperthyroxinemia. Break this up. When you say thyroxinemia, referring to your T4 in your blood; in this case, we have hyper. So, how could you possibly have a normal thyroid state and be hyperthyroxinemic? The discussion now brings us back to our physiologic point of view of thyroid binding globulin. Remember the definition of total? Total is bound plus free. What is the component that makes up majority of your total? It is the bound. So, therefore, euthyroid hyperthyroxinemia, due to, in general, increased binding protein. What is this specifically for thyroid hormone? Thyroid binding globulin. Coming from where? The liver. Your emphasis and focus should be on, well, what is then causing liver to increase is thyroid binding globulin. Before we go at there, abnormalities. T4 - binding. Majority of your T4 is bound thyroid binding globulin: 75%. Transthyretin: 15%. Albumin rounds it all up to approximately 15%. The most common cause - MCC of hyperthyroxinemia would be TBG excess. What is that going to do to your total? Total what? Total T4. Increases it. Why? What then binds to my TBG? T4 does. I’ll show you this. Remember, the majority of your thyroid hormone being released into circulation is T4. It has to be bound to TBG. Whenever TBG is found to be in...

    About the Lecture

    The lecture Euthyroid Hyperthyroxinemia – Euthyroid Conditions by Carlo Raj, MD is from the course Thyroid Gland Disorders.


    Included Quiz Questions

    1. Increased binding proteins
    2. Increased T4
    3. Increased conversion of T3 to T4, leading to decreased T3
    4. Decreased estrogen leading to decreased binding proteins
    5. Decreased albumin leading to increased TBG binding to T4
    1. Increased Estrogen
    2. Hepatitis
    3. Acute intermittent porphyria
    4. Amiodarone excess
    5. Methadone
    1. Progesterone only contraceptives
    2. Methadone
    3. Amiodarone
    4. Propanolol
    5. Zanoxifen
    1. Increased estrogen increases the level of TBG, decreases free T4 and leads to increased T4 production
    2. Increased estrogen increases the level of TBG, decreasing bound T3
    3. Delivery of thyroid hormone to the fetus decreases available thyroid hormone, leading to increased production
    4. Increased TBG due to decreased bound T4 leads to a spike in estrogen until TBG levels even out
    5. Decreased TBG due to increased delivery of T4 to the fetus leads to increased production of TBG
    1. 75%
    2. 16%
    3. 99%
    4. 15%
    5. 80%

    Author of lecture Euthyroid Hyperthyroxinemia – Euthyroid Conditions

     Carlo Raj, MD

    Carlo Raj, MD


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