| Pregnancy |
| Estrogen therapy |
| Weight gain |
| Drugs that increase catabolism of T4 |
| Rifampin |
| Carbamazepine |
| Phenytoin |
| Phenobarbital |
| Imatinib |
| Malabsorption or increased excretion of T4 |
| Gastrointestinal disorders (eg, celiac disease) |
| Impaired acid secretion |
| Drugs that interfere with T4 absorption |
| Ferrous sulfate |
| Cholestyramine or colestipol |
| Sucralfate |
| Aluminum hydroxide gels |
| Calcium carbonate |
| Sertraline |
| Raloxifene |
| Omeprazole |
| Nephrotic syndrome |
| Progressive thyroid dysfunction |
| Autoimmune thyroiditis |
| Previous thyroid irradiation |
