Euthyroid Hypothyroxinemia – Euthyroid Conditions

by Carlo Raj, MD

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    If the previous discussion was euthyroid hyperthyroxinemia, this discussion now brings us to euthyroid hypothyroxinemia. Euthyroid hypothyroxinemia due to, well, if the previous discussion was increased thyroid binding globulin, here you’re going to have decreased binding protein. So, you’ll have binding protein abnormalities. Let’s talk about those drugs. There are a bunch of drugs here that you want to know that will cause euthyroid hypothyroxinemia. Drugs that displace T4 from the binding site. So if you now displace your T4 from your TBG, what faction are you increasing here transiently? The free. Who is communicating with the hypothalamo-pituitary-thyroid axis? Is it the free or the bound? It’s the free. As far as you’re concerned to get any of your questions correct, it is the free T4 that is going to dictate how much thyroid functioning that you’re having in the body. Is that clear? In physiology, you’ve already talked about T4 and you have certain experts that’ll say, “Oh, no, no, no. It’s T3 that’s going to be responsible for feedback mechanism.” Both individuals are correct, as far as you’re concerned as a clinician. That T4, the free, is going to then regulate the feedback mechanism for your hypothalamus-pituitary and such. So, here, if you were displacing your T4 from your TBG, due to the drugs such as salicylates, such as furosemide in patients with CKI (stands for chronic kidney injury) patients, or NSAIDs such as mefenamic acid, then you’re removing the T4 from the bound. The free T4 that is found to be excess is going to slide down the axis. You’re in the state of euthyroid, but the total is decreased. Why? Because these drugs removed or displaced the T4 from your TBG. One important cause of euthyroid or one set of causes of euthyroid hypothyroxinemia. Let’s talk...

    About the Lecture

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

    Included Quiz Questions

    1. Propranolol
    2. Salicylates
    3. Furosemide in CKI patients
    4. NSAIDS
    5. Mefenamic acid
    1. Hereditary- X linked dominant
    2. Androgen excess
    3. Nephrotic syndrome
    4. Dunazol
    5. Niacin
    1. Heparin
    2. Phenytoin
    3. Carbamezapine
    4. Mefenamic acid
    5. L-asparaginase
    1. Decreased total thyroid hormone caused by an increase in free thyroid hormone due to decreased TBG
    2. Increased total thyroid hormone due to decreased TBG
    3. No change to thyroid hormone release but an increase in conversion from T4 to T3
    4. No change in thyroid hormone by down-regulation of TBG synthesis
    5. Increase in free thyroid hormone leading to a decrease in total thyroid hormone

    Author of lecture Euthyroid Hypothyroxinemia – Euthyroid Conditions

     Carlo Raj, MD

    Carlo Raj, MD

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