Thyroid Hormones S2M1

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Author:
lancesadams
ID:
89534
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Thyroid Hormones S2M1
Updated:
2011-08-12 19:15:06
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Ross S2M1
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Biochem
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  1. What is the apical transport for Iodine
    Pendrin
  2. Pendrin syndrome
    • Absence of Pendrin used for transporting Iodine into the follicular cells for thyroid hormones
    • It causes hearing problems and hypothyroidism
  3. What are the two essential ingredients to T3 and T4
    Protein bound tyrosine and iodine
  4. Iodine trap
    Active transport on the basal side of the follicular cells that transports Iodine and Na into the cell
  5. What are the ways that iodine can get into the follicular cells to make thyroid hormones
    • Pendrin transport
    • Iodine trap
    • Break down of MIT and DIT
  6. What the 7 steps for making T3 and T4
    • 1. ER in the Follicular cell makes Thyroglobulin then the Golgi glycosylates it
    • 2. Thyroglobulin is exocytosed into the lumen colloid
    • 3. Iodide is oxidized to Iodine by thyroperoxidase and binds to Thyroglobulin making MIT and DIT
    • 4. Binding of DIT and MIT makes protein bound T3 and T4
    • 5. Protein bound T3 and T4 are pinocytosed back into cell
    • 6. Hormones and thyroglobulin are separated by lysosymes
    • 7. MIT and DIT are recycled while T3 and T4 are released into blood stream
  7. Iodide is oxidized to Iodine by
    Thyroperoxidase
  8. What lies between follicular cells
    Tight junctions
  9. Thyroglobulin in the thyroid gland contains a supply of
    Hormone sufficient for three months
  10. How do T3 and T4 compare
    • T3 is 3-4 times more potent then T4
    • Half life of T4 is 6 days
    • Half life of T3 is 1.5 days
    • 95% of released hormone is T4
  11. How much of T3 and T4 is bound to proteins in the blood
    99%
  12. In large target tissues, what happens to the T4
    Some is activated to T3 and some to reverse T3 (rT3)
  13. Most of the T3 in the system comes from
    T4 broken down in tissues outside the thyroid gland
  14. What are the proteins that T3 an T4 are bound to in the blood stream
    • Thyroxin binding protein (TBG) (80%)
    • Transthyretin (10%)
    • Albumin (10%)
  15. What happens if a patient has a lack of Thyroxin binding globulin (TBG)
    The patient is normal, T3 and T4 will simply float around freely till it arrives at a target organ
  16. What benefit is the binding of the transport protein to T3 and T4
    • It has a longer half life
    • It can't be excreted while bound to a protein
  17. Transcortin
    Protein transport and binding agent for glucocorticoids
  18. What is the binding protein for Estrogens and Androgens
    Sex hormone binding globulin
  19. The biological action of a given hormone is proportional to
    The level of unbound hormone in the blood, not the total hormone
  20. The pituitary gland in the negative feedback system only recognizes
    Free Hormones
  21. Myxedema
    • Hypothyroidism in adults
    • - reduced metabolic rate
    • - Subcutaneous edema (caused by excess hyaluronic acid)
  22. What are the two most common endocrine issues
    Diabetes and Thyroid deficiency
  23. Hashimoto disease
    Autoimmune disease in which the thyroid is gradually destroyed
  24. In what geographical areas are people more prone to hypothyroidism and less prone, why
    • Prone in mountainous areas (lack of iodine)
    • Less prone near sea (its packed with iodine)
  25. What are the signs of hyperthyroidism
    • Increased metabolic rate
    • Palpitations
    • Restlessness
  26. What is it called when there is an enlargement of the thyroid gland
    Goiter
  27. What kinds of problems cause goiter
    • Iodine deficiency which causes a raise TSH levels
    • Antibody stimulating the thyroid (Graves disease)
  28. Wolff-Chaikoff affect
    High doses of iodine inhibit hormone release, used only for short term treatment
  29. What are some inorganic anions that inhibit iodine uptake into the thyroid gland
    • Thiocyanate
    • Nitrate
    • Pertechnetate

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