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52 Cards in this Set
- Front
- Back
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Where do thyroid hormones come from?
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T4(thyroxine) and T3 (triiodothyronine) production is an iodine dependent process. Iodine comes from dietary sources.
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What are sources of dietary iodine?
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Iodized salt
Seafood Coastal water Dairy products Meat Fruit Veggies all contain iodide where is it absorbed via the GI tract and the Thyroid oxidizes it to Iodine |
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What drug can inhibit iodide from entering the thyroid?
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Lithium
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How does iodine make T3 and T4? (iodide organification)
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Iodine + tyrosine combine to make monoiodotyrosine (MIT) and diiodotyrosine (DIT).
MIT + DIT =T3 DIT + DIT =T4. |
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What can inhibit iodide organification?
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Large doses of iodide and amiodarone
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What is the function of TSH?
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causes the release of T4/T3 into circulation
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What are the functions of T4/T3 on the CV system?
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-Increases heat production/O2 consumption (increases BMR)
-+inotrope and chronotropic effects |
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Hyperthyroidism
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Thyrotoxicosis is excess T4 and T3 most commonly caused by graves dz, Iatrogenic, thyroiditis (by virus or autoimmune)
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What is graves dz?
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Autoimmune dz resulting in thyroid stimulating antibodies that bind the TSH receptor and cause Increased thyroid hormones. TSH is undetectable.
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Amiodarone Induced Hyperthyroidism
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-3% of pts on amiodarone develop this
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What are the effects of T3 and T4 on the Pulmonary and Hypercapnic system?
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- Maintain the hypoxic/hypercapnic drive
-Increased production of epo |
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What are the effects of T3 and T4 on the GI system and skeletal system?
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-gut motility
-Bone turnover, resorption, formation |
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What are the effects of T3 and T4 on the Neuromuscular System?
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-synthesis of structural proteins, muscle contraction/relaxation
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What are the effects of T4 and T3 on Lipd/Carb Metabolism?
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-Glucose absorption, gluconeogenesis, glycogenolysis
-Cholesterol synthesis and degradation |
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What are the effects of T4 and T3 on the Endocrine system?
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-Metabolic turnover of hormones
-Cortisol, ovulation, prolactin |
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Signs/Symptoms of HYPERthyroidism
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-Heat Intolerance
-Weight Loss -Muscular Atrophy -Fatigue (also with HYPO) -Nervousness -Exophthalmos -Tachcardia -A fib |
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Signs/Symptoms of HYPOthyroidism
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-Cold Intolerance
-weight gain -dry coarse skin/hair -fatigue -Mental sluggishness -Anemia -growth retardation in children |
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What are the two drugs used in HYPERthyroidism?
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Methimazole (Tapazole)
Propylthiouracil (PTU) |
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MOA of Methimazole and PTU?
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They both inhibit thyroid peroxidase (T4/T3) synthesis, but only PTU inhibits the peripheral conversion of T4 to T3 as well
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Contraindications of Methimazole and PTU?
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MMI- Preg and breastfeeding
PTU- Preg |
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ADRs with Methimazole and PTU?
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fever, rash, arthralgias (joint pain)
Agranulocytosis (failure of the bone marrow to make enough WBCs), hepatitis |
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PTU dosing
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300-600mg divided 3-4 times/day
Max Dose: 1200mg/day Once sx begin to resolve (4-8 wks) dose should be tapered toward maintenance dose |
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Methimazole (Tapazole) Dosing
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Initial dose: 30-60mg divided 3x/day
MAX: 120mg/day Maintenance: 5-30mg per day |
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Do patients have to stay on PTU and Methimazole for the rest of their lives?
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No treatment lasts 12-24 months, then med is tapered and observed for return of sx
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Drug Interactions with MMI and PTU?
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By correcting the HYPERthyroidism, metabolism of clotting factors will be reduced resulting in a decreased response to warfarin
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What is INR?
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When monitoring warfarin you measure Prothrombin time in seconds. The INR is just the International Normalized Ratio used to compare prothrombin times.
INR should be between 2.0-3.0 unless you have a mechanical heart valve then it is between 2.5-3.5 |
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What does a high INR mean?
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It is taking the blood longer to clot (an increased warfarin effect)
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What should you tell a patient on warfarin?
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Minimize changes in intake of green leafy veggies, green peas, and oriental green tea.
These have vitamin K and will increase the warfarin efffect |
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How can HYPERthryoidism or high fever affect prothrombin time?
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expect a longer prothrombin time (higher INR)
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How does HYPOthyroidism affect prothrombin time?
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expect a shorter prothrombin time
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How does Vitamin K relate to warfarin?
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Vitamin K is necessary for production of clotting factors and anticoagulation proteins.
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What is the common treatment for Hypothyroidism?
Why do we treat? |
Levothyroxine (Synthetic T4)
QOL and decreases risk of atherosclerotic disease (LDL) |
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Is levothyroxine safe in Pregnancy and Lactation?
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Yes it is a category A
Minimal excretion in human milk |
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Counseling Points for levothyroxine?
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Take 30 min before breakfast on an empty stomach.
Complete resolution of symptoms may take several months, but should see improvement in 2-3 weeks |
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Liothyronine (Cytomel)
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Synthetic T3 generally reserved for myxedema or nontoxic goiter in Hypothroidism
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Why would Liothyronine be prescribed over Levothyroxine?
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Allows for more rapid suppression of TSH
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Disadvantages of Liothyronine over Levothyroxine?
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Liothyronine(cytomel) has a shorter half-life so divided dosing is usually required
Higher incidence of cardiac events more costly |
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Counseling Points for Liothyronine?
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Liotrix (Thyrolar)
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4:1 ratio of T4:T3
mimics natural secretion expensive |
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Counseling Points for Liotrix (Thyrolar)
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Dessicated Thyroid (Armour Thyroid)
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extracted from beef/pork thyroid gland
Unpredictable amount of hormone in each tablet |
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What should be monitored in Hypothyroidism patients?
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FT4
complete resolution of symptoms may take several months, but should see improvement in 2-3 weeks |
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How does hypothyroidism change during pregnancy?
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The dose of levothyroxine may increase as much as 25-50%
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what is Myedema Coma?
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End stage uncontrolled hypothyroidism...ICU
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Iatrogenic Hypothyroidism
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Occurs following exposure to radiation/surgery (usually treatment from hyperthyroidism)
No longer able to produce thyroid hormone Treatment of choide: levothyroxine |
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Hashimoto's Thyroiditis is what?
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gradual thyroid failure aand/or goiter due to auto-immune mediated destruction of the thyroid gland
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Treatment for Hashimoto's?
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same as Hypothyroid patient
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Subacute Granulomatous Thyroiditis (de Quervain's)
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inflammatory condition of the thyroid usually caused by a virus
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Symptoms of Subacute Granulomatous Thyroiditis (de Quervain's)
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anterior neck pain radiating to the ears, fever, malaise
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Treatment of Subacute Granulomatous Thyroiditis (de Quervain's)
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ASA, Prednisone, beta-blocker for Hyperthyroidism
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Subacute Lymphocytic Thyroiditis cause and treatment?
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Possibly auto-immune...manifests as autoimmune
Beta-blocker for hyperthyroidism |
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How does a beta-blocker help in hyperthyroidism?
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