Version July 2025
| Appropriate treatment of primary hypothyroidism |
| Assay interference with biotin ingestion |
| Binding protein abnormalities |
| TBG excess |
| Hereditary (rare) – TBG gene amplification, X-linked dominant |
| Acquired |
| Estrogen (including pregnancy, oral contraceptives, hormone therapy) |
| Other drugs (tamoxifen, raloxifene, methadone, heroin, 5-fluorouracil, clofibrate) |
| Hepatitis, acute or subacute |
| Acute intermittent porphyria |
| Familial dysalbuminemic hyperthyroxinemia |
| Abnormal transthyretin binding of T4 |
| Anti-T4 immunoglobulins (rare) – Can cause spuriously high T4 if measured by radioimmunoassay |
| Impaired conversion of T4 to T3 |
| Amiodarone |
| Ipodate and iopanoic acid (iodinated radiocontrast agents) |
| High-dose propranolol (>140 mg/day) |
| Other conditions |
| Acute nonthyroidal illness and psychosis |
| Generalized thyroid hormone resistance (TSH may be normal or slightly elevated; patients may be clinically euthyroid or have manifestations of hyper- or hypothyroidism) |
