Low caloric intake, malnutrition | The most common inhibitory factor of type 1 iodothyronine deiodinase (D1) |
Nonthyroid illness | Even if it is mild |
Drugs | |
Propylthiouracil | Not methimazole |
Glucocorticoids | Eg, 4 mg of dexamethasone decreases total T3 by 30% in several days |
Beta-adrenergic antagonists | Propranolol, metoprolol, atenolol, and alprenolol (not nadolol or sotalol) |
Oral cholecystographic agents (eg, sodium ipodate) | Not available in United States |
Amiodarone | Could compete with thyroxine (T4) for the deiodinative site |
Liver disease | Liver tissue expresses high levels of D1 |
Selenium deficiency | D1 is a selenoprotein |
Neonatal period | Especially in premature and low-birth-weight infants |