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27 Cards in this Set
- Front
- Back
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What are thyroid hormones used for in general? |
Normal Growth and Metabolism (Link with lipids) |
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Name of regulatory process |
Hypothalmic-pituitary-thyroid axis |
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Describe the gland |
Butterfly shape- 2 lobes Base of neck- surrounds trachea Lobes joined by skin called isthmus |
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Describe Histological Struture |
A follicle is made up of thyrocytes surrounding a colloid |
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Name 3 hormones thyrocytes produce |
Thyroxine - T4 Tri-idothyronine -T3 Reverse Tri-idothyronine -rT3 |
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Summarize thyroglobulin |
Glycoprotein Made in thyrocytes, exported to the colloid Carries 70% of bound T4 and T3 in blood |
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Describe Iodines role |
I- is actively taken into the cell with Na+ Iodide is the transported to colloid by Pendrin Iodide is then put into thyroglobulin by thyroid peroxidase generating T3, T4 or rT3 |
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What is TRH and what does it do? |
Thyrotropin release hormone Secreted from hypothalamus Stimulates pituitary gland to secrete TSH |
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What is TSH and what does it do? |
Thyroid stimulating hormone Secreted from pituitary gland Stimulated thyroid to secrete T4 and T3 |
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What is T4 and T3's role in the feedback mechanism? |
T3 and T4 inhibit the secretion of TRH and TSH |
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Describe the activity of T3 and T4 |
T3 is the active hormone as it binds to cells and triggers responses T4 can be metabolised to to rT3 which is biologically inactive |
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How is 2/3 of T3 produced? |
Kidneys and liver detonate T4 to produce T3 |
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What receptors does T3 bind to and what does this induce? |
Retinoid X Receptors (RXR) Stimulates gene expression and synthesis of polypeptides hormones and enzymes |
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How is T3 and T4 excreted? |
Deiodination Metabolism Conjugated in liver and excreted in bile |
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What is usually tested in a thyroid function test? |
TSH and Free T4 |
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Name some other tests used? |
TSH immunological assay TRH Test Anti-thyroid peroxidase antibodies |
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What are newborns screened for and how? |
Hypothyroidism TSH measured in heel prick test Results in cretinism if not treated |
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Describe Hypothyroidism |
Underachieve thyroid gland Develops slowly Easy to miss Primary- failure of gland itself Secondary- Failure of pituitary to secrete TSH |
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Symptoms of Hypothyroidism |
Goitre Cool extremities Bradycardia Dry skin Cold intolerance Constipation Weight gain |
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Causes of Hypothyroidism |
Primary- Hashimotos Disease Secondary- Tumours/head injury |
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Describe Hashimoto's Disease |
Autoimmune Free t4 is low TSH is raised Selection of anti-thyroid peroxidase Ab's Treated with thyroid replacement therapy |
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Describe Hyperthyroidism |
Overactive thyroid gland Aka thyrotoxixosis Common causes - Graves Disease and Toxic multi nodular goitre |
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Describe Hyperthyroidism Symptoms |
Heat intolerance Palpitations Loss of weight Increased bowel movement Goitre Tachycardia |
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Grave's Disease |
Auto-immune Antibiotics bind to TSH receptor to mimic the TSH action Regulation is lost TSH is inhibited due to high T4 and T3 in blood Eyelid retraction ans TSH receptor and orbital muscle have a common Ag |
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Toxic Multi-Nodular Goitre |
Iodine deficiency ---> decreased T4 production Induction of thyroid cell hyperplasia via Receptor mutations |
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Diagnosis of Hyperthyroidism |
Low TSH Free T3 increase Goitre |
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Treatment of Hyperthyroidism |
Anti-thyroid drugs- Methimazole Beta- blockers for tachycardia Surgery of thyroid Hormone replacement therapy |
