Related DDx ⬇
Etiology ⬆
- Primary hypothyroidism
- "Subclinical" hypothyroidism: high TSH, clinically euthyroid, normal T4
- Autoimmune disease (assay interference)
- Recovery from nonthyroidal illness
- Acute psychiatric illness
- Drugs: dopamine antagonists (eg, metoclopramide), phenothiazines, atypical antipsychotics
- Levothyroxine malabsorption due to iron, sucralfate, aluminum hydroxide antacids, calcium supplements, soy milk
- Rare cases of hyperthyroidism due to inappropriate pituitary TSH secretion, eg, neoplasm