thyroid hormones and anti-thyroid drugs - ISpatula:甲状腺激素及抗甲状腺药物ispatula.ppt
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Inhibition of thyroid hormone synthesisThioamides They have a slow onset of pharmacological effect Since the synthesis rather than the release of hormones is affected, the onset of these agents is slow (3-4 weeks) before stores of T4 are depleted Anion inhibitors Monovalent anions: perchlorate (ClO4–), pertechnetate (TcO4–), and thiocyanate (SCN–) MOA: block uptake of iodide by the gland through competitive inhibition of the iodide transport mechanism Clinical uses: block thyroidal reuptake of I– in patients with iodide-induced hyperthyroidism (eg, amiodarone-induced hyperthyroidism) Potassium perchlorate is rarely used clinically because it is associated with aplastic anemia Inhibition of hormone releaseIodides The effects of iodide on the thyroid gland are complex: Inhibit hormone release, possibly through inhibition of thyroglobulin proteolysis (major) Inhibit organification Decrease the size and vascularity of the hyperplastic gland Improvement in symptoms occurs rapidly—within 2–7 days Iodides Clinical Uses Treatement of severe thyrotoxicosis or thyroid crisis when a rapid decrease in plasma T4 and T3 is desirable Preoperative preparation of patients about to undergo total or subtotal surgical thyroidectomy Iodide Iodide should not be used alone Iodide should not be used alone, because the gland will escape from the iodide block in 2–8 weeks, and its withdrawal may produce severe exacerbation of thyrotoxicosis in an iodine-enriched gland Iodide use should be initiated only after onset of thioamide treatment not used if radioactive iodine therapy is planned Chronic use of iodides in pregnancy should be avoided Radioactive Iodine (131I) Used for treatment of thyrotoxicosis 131I is taken up and trapped in the same manner as I-.The ablative effect is exerted primarily through β- particle emissions, which destroy thyroid tissue Advantages: easy administration, effectiveness, low expense, and absence of pain Major disadvantage is the develo
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