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37 Cards in this Set
- Front
- Back
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Levothyroxine and half life
SE |
T4 Analog
t 1/2 = 7 days |
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Liothyronine and half life
SE |
T3 Analog
t 1/2 = 1 day Greatest risk of <3 toxicity |
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Liotrix
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T3/T4 mixtures 1:4
NOT really used anymore $$$$ |
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Inidications for Levothyroxin
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Safe to use during pregnancy (may need to increase dosage)
Lifelong treatment |
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OD on Thyroid
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nervousness, tachy, angina, arrhythmias <3 failure, osteoporosis due to Ca loss
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4 Categories of Rx for Hyperthyroidism
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1. modify production of thyroid hormones
2. block iodine uptake 3. modify tissue response 4. destroy thyroid gland |
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THIOAMIDES
examples |
propylthiouracil, methimazole, carbimazole (UK)
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THIOAMIDES
MOA |
fxn: bind thyroperoxidase (TPO) compettivitely and inhibit iodide incorporation into coupling
***does NOT block uptake of I or release of thyroid hormones |
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Propylthiouracil
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inhibits 5-deiodinase, thus inhibits T4 -> T3 in addition to inhibit I incorporated
***does NOT block uptake of I or release of thyroid hormones |
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Propylthiouracil
Pros/Cons |
Pro: preferrable in pregnancy
Con: t1/2 = 1.5 hrs (dose 6-8x) agranulocytosis, jaundice, sore throat |
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Methimazole
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longer half life (t1/2 6 hrs)
like others in class takes a month to show results bc synthesis is affected not release of hormones |
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Risk with PTU
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liver damage, failure and death
CI: peds patients |
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ANIONIC INHIBITORS
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perchlorate
thiocyanate pertechnetate |
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Anionic Inhibitors
MOA |
BLOCK IODIDE UPTAKE by thyroid gland, compete with iodide for sodium iodide symporter & displace iodide
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Use of Anionic Inhibiotors
Contraindicated |
Use; amiodarone induced hyperthyroidism
CI: aplastic anemia |
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Radioiodide I131
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accumulates in thyroid, B particles destroy surrounding tissue
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Consequences of Radioiodide I131
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Hypothyroidism occurs 80%
ppt thyroid storm not for pregnant, ppl < 21 Iodide should be avoided Pre-treat with methimazole |
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Iodide
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Inhibit TPO, colloid resorption, and proteolysis of thryoglobulin
Rx: thyroid storm reduce size/vasc of thyroid prior to thyroidectomy |
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DEIODINASE INHIBITORS
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BLOCK T4 --> T3 conversion
Iodinated Contrasting Agents Corticosteroids (Dexamethasone) B Blockers (Propanol) PTU |
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Adrenoreceptor Blocking Agents
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Propranol & Guanethidine
treats sx does not eliminate cause in thyroid storm: |
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Propranol
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propranol can help protect against serious cardiac arrhythmias
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Guanethidine
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noradrenergic blocker to ameliorate exophthalmos
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Thyroid Storm Treatment
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Sx: fever, tachy, arrhythmias, sweating, extreme weight loss
Bblockers to control CVS; PTU or MMI to block synthesis of new thyroid hormones; dex protects against shock AVOID Aspirin |
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May cause hyperthyroidism or hypothyroidism
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Amiodarone
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Blocks iodide uptake
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Perchlorate
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Iodine rich anti-arrhthymic agent
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Amiodarone
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Iodinated contrasting agent that blocks T4 to T3 conversion
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Iopanoic Acid
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anionic inhibitor that blocks iodide uptake
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perchlorate
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may cause irreversible hypothyroidism
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radioiodide
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What is the final step of T3 synthesis? Where does this occur?
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○ The final step in all of this occurs in the periphery. It occurs in the liver and other tissues. And what occurs is there is an enzyme called iodothryonine deiodinase and this enzyme in the peripheral tissue will now take T4 and by removing the 5' iodo group will convert this to T3.
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The thyroglobulin iodinated tyrosines. Some of these are next to one another - diiodotyrosines and others are monoiodotyrosines. How do these pair to form T4 and T3?
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T4 is formed from two diiodotyrosines and T3 is formed from one diiodotryosine and one monotryosine.
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types of hypothyroidism
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Hashimotos
Endemic, myxedema (adults), cretinism (fetal) |
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types of hyperthyroidism
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Toxic nodular goitre, grave's, carcinoma, thyrotoxicosis
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iodine clinical uses
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Preoperative preparation for thyroidectomy, use after radio therapy, protection after radio exposure, treatment of endemic goitre
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Can be effective for short term therapy of thyroid storm, but after several weeks of therapy causes an exacerbation of hyperthyroidism
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iodide salts
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two iodines at c3 and c5 in t3 and t4 restrict roation of the two phenolic rings...creating
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active conformation
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upon proteolysis and secretion, a thyroglobulin dimer yields only...
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2-4 molecules of t4 and t3
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