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37 Cards in this Set
- Front
- Back
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anions which inhibit Na+I- transporter into thyroid gland
BRS Phys |
Thiocyanate
Perchlorate |
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process iodinating tyrosine residues within thyroglobulin
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iodine organification
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patients who should recieve lower doses of Levothyroxine
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Elderly
Cardiovascular disease Longstanding hypothyroidism all are more sensitive to effects |
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Thioamides available
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Propylthiouracil (PTU)
Methimazole |
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Thioamide which inhibits peripheral T4 to T3 conversion in addition normal actions (↓peroxidase, organification, coupling)
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Propylthiouracil
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Onset of thioamide effect
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3 to 4 weeks, no inhibition of release of preformed hormone
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Thioamide preferred in pregnancy
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Propylthiouracil
less likely to cross BBB, has ↑protein bound % |
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Most common SE of Thioamides
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Skin rash
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Onset of action of Iodides
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2-7 days
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Clinical use of Iodides
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Thyroid Storm
Surgical preparation |
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Lugols Solution
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Iodide + Potassium
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MOA of Iodides
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inhibit iodination of tyrosine and thyroid hormone release
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Drug which can produce a permanent cure to thyrotoxicosis
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Radioactive Iodine
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Containdication of radioactive iodine
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Pregnancy or nursing women
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Toxicity of perchlorate
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aplastic anemia
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most important drug in thyrotoxicosis
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propanolol
ß effects as well as decreasing peripheral conversion of T4 to T3 |
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Thyroid effects of Amiodarone
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Hypothyroid by inhibiting peripheral T4 to T3 conversion
Hyperthyroid in patients with underlying thyroid diseases |
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Most widely used thyroid drugs such as Synthroid and Levoxyl contain
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L-thyroxine (T4)
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T3 compound less widely used
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Cytomel
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Antithyroid drugs
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Thioamides
Iodies Radioactive Iodine Ipodate |
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Thioamide agents used in Hyperthyroidism
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Methimazole
Propylthiouracil (PTU) |
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Thioamide less likely to cross placenta, inhibits peripheral conversion of T4 to T3 in high doses, and should be used with extreme caution in pregnancy
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PTU
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PTU MOA
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Inhibits thyroid hormone synthesis by blocking iodination of the tyrosine residues of thyroglobulin
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Can be effctive for -short term- therapy of thyroid storm, but after several weeks of therapy causes and exacerbation of hyperthyroidism
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iodide salts
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dose may need to be increased during pregnancy or with OCs due to increased TBG in plasma
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Thyroxine
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-Permanently- cures thyrotoxicosis, patients will need thyroid replacement therapy thereafter
contraindicated in pregnancy |
Radioactive iodine
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Radiocontrast media that inhibits the conversion of T4 to T3
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Ipodate
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Block cardiac adverse effects of thyrotoxicosis such as tachycardia, inhibits the conversion of T4 to T3
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Beta blockers such as propranolol
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Vitamins containing iron should NOT be taken simultaneously with levothyroxine because
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Iron deiodinates thyroxine
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Thyroxine dose may need to be increased in hypothyroid patient during pregnancy because
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Estrogens increase materal TBG
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Steroid effect on TBG
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Decrease
will have normal Free T4, elevated total T4, normal TSH |
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inhibit organification of iodide and coupling of thyroid hormone synthesis
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Propylthiouracil and Methimazole
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addition effect of propylthiouracil
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↓ peripheral conversion of T4 to T3
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Toxicity of Thioamides
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Skin rash
agranulocytosis (rare) aplastic anemia methimazole teratogen |
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Thyroxine replacement
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levothyroxine
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Toxicity of levothyroxine
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Tachycardia
heat intolerance tremors arrhythmia |
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risk of administering levothyroxine in elderly with longstanding hypothyroidism?
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overstimulation of heart
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