| Low serum TSH |
| Primary hyperthyroidism |
| Incomplete recovery from hyperthyroidism |
| Nonthyroidal illness |
| High levels of chorionic gonadotropin - early pregnancy, molar pregnancy, choriocarcinoma |
| Drugs - dopamine agonists, glucocorticoids, somatostatin analogs |
| Central hypothyroidism |
| High serum TSH |
| Primary hypothyroidism |
| Recovery from nonthyroidal illness |
| Drugs - dopamine antagonists, amiodarone, oral cholecystogram dye (sodium ipodate) |
| TSH-producing pituitary adenoma |
| Adrenal insufficiency |
| Heterophilic antibody interference |
| Generalized thyroid hormone resistance |
