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Figures
- Figure 1
Early and late stages of amiodarone-induced thyrotoxicosis (AIT). (A) In early AIT, amiodarone blocks the conversion of thyroxine (T4) to triiodothyronine (T3), leading to increased levels of T4 and decreased levels of T3. Through feedback, the pituitary gland is stimulated to produce more thyroid-stimulating hormone (TSH), which promotes thyroid hormone production by the thyroid gland. (B) In late AIT, after the increased TSH production and stimulation of the thyroid gland, T3 and T4 levels both become elevated. Through negative feedback on the pituitary gland, less TSH is secreted.
Tables
Type 1 AIT Type 2 AIT Mixed AIT Mechanism of disease Excess iodine Destructive inflammatory thyroiditis Features of both Underlying thyroid disease Present Absent Features of both Goiter Multinodular or diffuse goiter normally present Infrequent; may have small, diffuse, firm, or tender goiter Features of both TSH, early disease course Elevated Normal Variable TSH, late disease course Elevated Normal Variable Thyroid autoantibodies Present Absent Features of both Radioactive iodine studies Normal or increased uptake Little or no update Features of both 99mTc-MIBI Increased uptake Decreased uptake Features of both Color-flow Doppler ultrasonography High vascularity Absent vascularity Features of both Treatment Thionamides Steroids Combination of both Spontaneous remission No Possible Features of both Late hypothyroidism No Extremely rare Features of both 99mTc-MIBI = technetium Tc 99m methoxyisobutylisonitrile; TSH = thyroid-stimulating hormone
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