Treatment-refractory hypothyroidism: Don't just increase the dose.

Causes of treatment-refractory hypothyroidism include nonadherence, interference from food or drugs, gastrointestinal disorders, and increased levothyroxine turnover. A practical, stepwise diagnostic approach starts with a detailed history, followed by gastrointestinal and ancillary evaluations. Assay interference and other confounding conditions should also be considered. A trial of levothyroxine formulations other than oral tablets may be useful in select cases.