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37 Cards in this Set

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anions which inhibit Na+I- transporter into thyroid gland

BRS Phys
Thiocyanate
Perchlorate
process iodinating tyrosine residues within thyroglobulin
iodine organification
patients who should recieve lower doses of Levothyroxine
Elderly
Cardiovascular disease
Longstanding hypothyroidism

all are more sensitive to effects
Thioamides available
Propylthiouracil (PTU)
Methimazole
Thioamide which inhibits peripheral T4 to T3 conversion in addition normal actions (↓peroxidase, organification, coupling)
Propylthiouracil
Onset of thioamide effect
3 to 4 weeks, no inhibition of release of preformed hormone
Thioamide preferred in pregnancy
Propylthiouracil

less likely to cross BBB, has ↑protein bound %
Most common SE of Thioamides
Skin rash
Onset of action of Iodides
2-7 days
Clinical use of Iodides
Thyroid Storm
Surgical preparation
Lugols Solution
Iodide + Potassium
MOA of Iodides
inhibit iodination of tyrosine and thyroid hormone release
Drug which can produce a permanent cure to thyrotoxicosis
Radioactive Iodine
Containdication of radioactive iodine
Pregnancy or nursing women
Toxicity of perchlorate
aplastic anemia
most important drug in thyrotoxicosis
propanolol

ß effects as well as decreasing peripheral conversion of T4 to T3
Thyroid effects of Amiodarone
Hypothyroid by inhibiting peripheral T4 to T3 conversion

Hyperthyroid in patients with underlying thyroid diseases
Most widely used thyroid drugs such as Synthroid and Levoxyl contain
L-thyroxine (T4)
T3 compound less widely used
Cytomel
Antithyroid drugs
Thioamides
Iodies
Radioactive Iodine
Ipodate
Thioamide agents used in Hyperthyroidism
Methimazole
Propylthiouracil (PTU)
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
PTU
PTU MOA
Inhibits thyroid hormone synthesis by blocking iodination of the tyrosine residues of thyroglobulin
Can be effctive for -short term- therapy of thyroid storm, but after several weeks of therapy causes and exacerbation of hyperthyroidism
iodide salts
dose may need to be increased during pregnancy or with OCs due to increased TBG in plasma
Thyroxine
-Permanently- cures thyrotoxicosis, patients will need thyroid replacement therapy thereafter

contraindicated in pregnancy
Radioactive iodine
Radiocontrast media that inhibits the conversion of T4 to T3
Ipodate
Block cardiac adverse effects of thyrotoxicosis such as tachycardia, inhibits the conversion of T4 to T3
Beta blockers such as propranolol
Vitamins containing iron should NOT be taken simultaneously with levothyroxine because
Iron deiodinates thyroxine
Thyroxine dose may need to be increased in hypothyroid patient during pregnancy because
Estrogens increase materal TBG
Steroid effect on TBG
Decrease

will have normal Free T4, elevated total T4, normal TSH
inhibit organification of iodide and coupling of thyroid hormone synthesis
Propylthiouracil and Methimazole
addition effect of propylthiouracil
↓ peripheral conversion of T4 to T3
Toxicity of Thioamides
Skin rash
agranulocytosis (rare)
aplastic anemia

methimazole teratogen
Thyroxine replacement
levothyroxine
Toxicity of levothyroxine
Tachycardia
heat intolerance
tremors
arrhythmia
risk of administering levothyroxine in elderly with longstanding hypothyroidism?
overstimulation of heart