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THYROID

THYROID . By Joshua Bower Easter Revision 2014 J.Bower@warwick.ac.uk. What hormones does the thyroid gland produce?. Thyroxine (T4) Tri- iodothyronine (T3) Calcitonin. List the SIX steps in thyroid hormone synthesis [6]. Thyroglobulin synthesised from tyrosine

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THYROID

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  1. THYROID By Joshua Bower Easter Revision 2014 J.Bower@warwick.ac.uk

  2. What hormones does the thyroid gland produce? • Thyroxine (T4) • Tri-iodothyronine (T3) • Calcitonin

  3. List the SIX steps in thyroid hormone synthesis [6] • Thyroglobulin synthesised from tyrosine • Uptake and concentration of iodide • Oxidation of iodide to iodine • Iodination of thyroglobulin • Coupling of 2 iodinated tyrosine molecules to form T4 or T3 • Secretion

  4. Thyroid Hormone synthesis (3) Thyroglobulin chain (tyrosine residues) hydrolysis Secretion T3 & T4 Conjugation MIT and DIT T3 and T4 MIT and DIT mono-, di-iodotyrosine Follicular Lumen (COLLOID) Blood Thyroglobulin synthesis iodine(Io) TPO NIS Iodide (I-) pendrin Follicle cell

  5. Describe the HPT axis

  6. How do thyroid hormones travel? • 70% bound to thyroxin binding globulin (70%) • 30% bound to albumin • TBG has higher affinity for T4 – readily available reserve

  7. Which hormone is the active one? • T3 • T4 is converted by deiodinases to T3, to bind to T3R and have an effect

  8. List FOUR physiological actions of TH [4] • Affects BMR • Maturation and differentiation of bone, lung, brain etc • Synapse formation • Myelinogenesis • Neuronal outgrowth • Growth (regulated by GH, but needs T3/T4)

  9. By what week of development does the foetus make its own T3/T4? • Week 12 • After trimester 1, not enough TSH or T4/T3 can cross placenta

  10. What is cretinism? • Impaired physical and neurological development due to iodine deficiency during foetal or postnatal development • Irreversible after first 2 years of life • TSH levels tested for in heel prick test

  11. List THREE signs/symptoms of hyperthyroidism [3]

  12. What would the blood test results show in hyperthyroidism? • Inc’dT3/T4 • Inc’d TSH (if fault in or above pituitary gland) • Dec’d TSH (if fault with thyroid gland)

  13. What is Grave’s disease? • Auto-antibody (TSI) for the TSH receptor • Causes hyperthyroidism • Causes goitre as TSI is stimulating thyroid gland, even if TSH levels low

  14. List THREE signs/symptoms of hypothyroidism [3] • Slow • Lethargic • Overweight/obese • Alopecia • Goitre

  15. What would the blood test results show in hypothyroidism? • Dec’d T3/T4 • Inc’d TSH (usually)

  16. List THREE possible treatments for thyroid issues [3] • Drugs (inhibit production or replace hormone) • Radioactive iodine (131I) to destroy gland • Surgery

  17. List THREE complications associated with thyroid gland surgery [3] • General surgery issues • Vocal cord nerve damage • Bleeding • Parathyroid gland damage

  18. QUESTIONS? By Joshua Bower Easter Revision 2014 J.Bower@warwick.ac.uk

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