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What are the two active thyroid hormones?
Thyroxine (T4) and Triiodothyronine (T3)
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What enzyme catalyzes the removal of one iodine from T4 to give T3?
5'-deiodinase
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Where does the majority (80%) of T3 come from?
T4
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What are 5 actions of TSH?
- 1. increase blood flow
- 2. I- uptake
- 3. T3/T4 synthesis
- 4. T3/T4 release
- 5. hypertrophy (goiter)
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How do T3/T4 affect growth and development?
increase protein synthesis
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What effect does T3/T4 have on the cardiovascular system?
increase HR and CO (increase beta adrenoreceptors)
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What effect does T3/T4 have on the central nervous system?
increases activity and awareness
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What are the metabolic effects of T3/T4?
increase CHO metabolism and increase lipolysis
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What is the most common etiology of Hypothyroidism?
Autoimmune thyroiditis (Hashimoto's disease)
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What is the name of primary thyroid deficiency in children?
cretinism
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What is the name of primary thyroid deficiency in adults?
myxedema
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What are two causes of cretinism?
endemic (not enough iodine in diet) and athyrotic (genetic disorder)
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What are the four treatment options for hypothyroidism?
- Thyroid powder
- Levothyroxine sodium (T4)
- Liothyronine sodium (T3)
- Liotrix (T4:T3 / 4:1)
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What would you administer to treat an emergency case of hypothyroidism?
liothyronine sodium (T3)
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When treating hypothyroidism, patients with what diease should you be cautious of?
cardiovascular disease
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What side effects do hypothroidism treatments have on the CNS, cardiovascular system, and metabolic rate?
- CNS: nervousness, insomnia, increase activity
- CV: hypertension, cardiac dysrhythmias
- Metabolic: increase BMR
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What are 3 thiourylenes?
- Propylthiouracil (PTU)
- Methimazole
- Carbimazole (not used in US)
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What do thiourylenes treat?
Hyperthyroidism
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What is the mechanism of action for thiourylenes?
block activity of peroxidase enzyme
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What are 5 side effects of thiourylenes?
- rash
- nausea
- headahce
- joint pain
- agranulocytosis
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Which thiourylene has less compliance with patients?
Propylthiouracil (PTU) due to its shorter half-life (2 hours)
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What are 5 treatment options for hyperthyroidism and/or its symptoms?
- thiourylenes
- radioactive iodine
- thyroidectomy
- iodide
- beta-adrenorecptor antagonsists (propranolol)
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What are adverse effects to a thyroidectomoy?
- hypothyroidism
- hypoparathyroidism
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Why are antithyroid agents not the best option for treatment of hyperthyroidism?
they can lose their effectiveness over time
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Which isotope of iodine is used in radioactive iodine treatment of hyperthyroidism?
131I
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