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65 Cards in this Set
- Front
- Back
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What are the 4 thyroid agents to know?
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-Levothyroxine
-Liothyronine -Liotrix -Thyroglobulin |
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What are the 5 Anti-thyroid drugs to know?
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-Iodide
-Radioactive iodine -Ipodate -Methimazole -Propylthiouracil (PTU) |
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What is the purpose of the T3/T4 that the thyroid gland normally secretes?
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Maintainence of normal growth and development, Metabolism, and Cardiac function.
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Where do we get our iodide?
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From the diet
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How is Iodine transported from the bloodstream into thyroid follicular cells? What is the effect of this mechanism?
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By a Na/I symporter - concentrates Iodine to 20-50X higher in the thyroid
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What happens to Iodine after uptake into the thyroid follicular cell?
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Organification by the enzyme PEROXIDASE
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What is the product of iodine organification?
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OI
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What happens to OI?
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It gets attached to tyrosines on thyroglobulin and incorporated into the protein.
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What is the product of incorporating IO into thyroglobulin?
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MIT and DIT
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What happens to MIT and DIT?
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Coupling to produce T3/T4
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Where is T3/T4 stored?
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In the colloid, bound to Thyroglobulin
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How does T3/T4 get out of the colloid when needed?
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By endocytosis and proteolysis from thyroglobulin
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What transports T3/T4 in the circulation?
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TBG - T3/T4
Transthyretin - T4 only |
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What is there more of; T3 or T4?
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T4 - 95%
T3 - 5% only |
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Which is the more potent thyroid hormone? Why?
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T3 by far - it has higher affinity for the thyroid hormone receptor
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What enzymes convert T4 to T3 at the peripheral tissue sites?
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D1, D2, and D3 - Iodothyronine 5' deiodinases
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What does T3 do?
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Diffuses into target cells, binds its receptor and regulates gene expression.
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And what are the 3 things that Thyroid hormone functions in regulating?
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1. Optimal growth/function, development, body tissue maint.
2. Cardiac function 3. Metabolism of carbs/fats and drugs |
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What are 3 things that stimulate release of TRH from the hypothalamus?
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Cold
Acute psychosis Circadian and Pulsatile rythms |
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What inhibits release of TRH from the hypothalamus?
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Severe stress
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What is the primary controller of thyroid hormone synthesis and secretion?
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TSH
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What inhibits release of TRH and TSH?
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NFB from T3/T4
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What is the primary AUTOregulator of the thyroid?
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Mechanisms WITHIN the thyroid that respond to iodine levels in the blood.
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How do blood Iodine levels affect thyroid hormone production?
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LOW levels stimulate it
HIGH doses INHIBIT IT! |
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What are LATS?
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ABnormal thyroid stimulators called Long Acting Thyroid Stimulators
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What is an example of an LATS?
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TSI - thyroid stimulating immunoglobulin in Graves
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What are 4 things that inhibit the anterior pituitary from releasing TSH?
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-Corticosteroids
-Dopamine -Somatostatin -Stress |
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What determines how responsive a tissue will be to blood levels of T4?
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The number of receptors that it has
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Most sensitive test for primary hypothyroidism and hyperthyroidism:
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TSH
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What will TSH levels be in hypothyroidism?
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High in primary
Low in secondary |
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What should happen to a normal person's TSH levels when given an injection of TRH in a TRH test?
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TSH levels should rise 2-4X
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If TSH levels do not rise, what might this be indicative of?
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Early hyperthyroidism
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What will radiolabeled iodine uptake scan show in hyperthyroidism?
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Diffusely increased uptake
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What will radiolabeled iodine uptake scan show in benign vs malignant nodules?
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Benign: hot nodules (increased uptake)
Malignant: cold nodules (no increased uptake) |
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What is the best diagnostic method for thyroid cancer though?
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FNAB - fine needle aspiration biopsy
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What is hypothyroidism in infants?
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Cretinism
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What is the reason that an infant with cretinism will usually present?
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Failure of development - dwarfism and mental retardation
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What is the txmt for Cretinism?
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Replacement therapy
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What happens to adults that are hypothyroid?
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Dwarfism and mental retardation
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Really?
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no I was just distracted
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So symptoms of hypothyroidism in adults:
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Reversible slowing of all body functions
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What is the most common cause of hypothyroidism in adults in the USA?
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Hashimoto's thyroiditis
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What is hashimoto's thyroiditis?
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Autoimmune destruction of the thyroid due to an autoantibody
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Will a goiter be seen in Hashimoto's?
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Early, but absent later.
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What used to be the treatment for hypothyroidism?
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Thyroglobulin from pig extract
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Why isn't pig thyroglobulin (or dessicated thyroid) used anymore?
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Because of instability and antigenicity
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What are the 3 replacement hormones for hypothyroidism now?
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-Levothyroxine
-Liothyronine -Liotrix |
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Which drug is the drug of choice for replacement and suppression therapy?
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Levothyroxine
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Why is levothyroxine the drug of choice?
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Because it is T4 - it lets the body decide when/where to activate it to T3
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How is Liothyronine different from Levothyroxine?
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-Shorter duration of action
-NOT recommended for routine replacement therapy - it is T3 |
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What is Liotrix?
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A mixture of T4:T3 in a 4:1 ratio
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What is the result of the mixture in Liotrix?
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Resembles normal secretion from the thyroid gland.
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What will the symptoms of adverse reactions to thyroid hormone replacement be similar to?
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Hyperthyroidism -
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What is a specific adverse reaction to thyroid hrt?
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Increased catabolism of VitK dep clotting factors
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What are 4 major problems we run into in treating Hypothyroidism?
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-Myxedema
-Myxedema and CAD -Myxedema coma -Pregnancy |
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What is myxedema?
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The accumulation of mucopolysaccharide in the skin and visceral sites resulting in non-pitting edema
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For which patients with Myxedema do you especially have to treat with caution? Why?
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Elderly - they often have underlying coronary artery disease (CAD)
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Why must you be cautious treating elderly patients with myxedema and CAD?
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If you give too much levothyroxine too fast, you may precipitate angina or arrythmia
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Because of the caution you have to use in treating old people with myxedema/CAD, what might you have to settle for?
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Never really restoring them to a completely euthyroid state.
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What is the end state of untreated hypothyroidism?
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Myxedema coma
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What is seen in Myxedema coma? (5 symptoms) What does it ultimately end in?
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-Progressive weakness
-Stupor -Hypothermia/glycemia/natremia Ultimate end: shock/death |
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Why does Myxedema coma develop when hypothyroidism is untreated
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Bc of the lack of metabolism resulting in CO2 retention, hypoxia, and marked hypothermia
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What are the 2 drugs to give in treating the medical emergency of Myxedema coma?
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-Levothyroxine
-Hydrocortisone |
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What is the deal with Hypothyroidism and pregnancy?
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You have to MAKE SURE the mom is on T3/T4 replacement so the baby's brain develops normally.
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What are 2 tests needed for monitoring the thyroid status in a pregnant woman? Why?
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FT4 and TSH - bc the maternal TBG levels will be elevated, so the FT4 levels may appear low
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