Ricerc@Sapienza

Background: Levothyroxine sodium (LT4) is the therapy of choice for hypothyroidism.
In the last decade, new LT4 formulations, such as liquid and softgel capsules, became
available. Even if some evidence has been reached in the efficacy of liquid LT4 in patients
with suboptimal TSH on tablet LT4, the usefulness of softgel LT4 has been rarely studied.
This study aimed at evaluating the effect of switching from tablet to softgel LT4
patients without increased need for LT4. TSH was used as proxy of LT4 bioavailability
and effectiveness.

Levothyroxine (T4) is a critical-dose drug, because little variations in the blood concentration may cause treatment failure as well as iatrogenic thyrotoxicosis. Despite the dose response of this drug being more carefully titrated nowadays, several papers still report that a significant fraction of patients treated with levothyroxine demonstrate a TSH which is not on target. Moreover, some widespread gastrointestinal disorders as well as interfering drugs and foods may cause the “refractoriness” of a significant number of patients to an expected dose of thyroxine.