PURPOSE

Since the introduction of an ethanol-free liquid levothyroxine formulation, only few studies assessed its therapeutic efficacy. The present study aimed to compare the efficacy of tablet (T-LT4) versus L-EF-LT4 in achieving the patient-specific TSH target in thyroidectomized patients. The primary objective was to assess whether the required LT4 dose differed between formulations in a real-life setting.

METHODS

The study was conducted on 275 patients who underwent total thyroidectomy and were treated with either T-LT4 (n = 152) or L-EF-LT4 (n = 123) between 2020 and 2023. Clinical and biochemical data, including LT4 dose, BMI, TSH levels, and potential causes of malabsorption, were collected. The primary endpoint was the pro-kg LT4 dose required to achieve individualized TSH targets. Multivariate regression analysis was used to evaluate predictors of LT4 requirement.

RESULTS

At final follow-up, 227 patients (82.5%) achieved their TSH target and were under stable doses of LT4 with no significant difference in mean LT4 dose between groups (T-LT4: 1.54 ± 0.35 µg/kg/day; L-EF-LT4: 1.60 ± 0.32 µg/kg/day, p = 0.160). TSH levels were comparable (p = 0.311). Regression analysis showed that age and BMI were inversely correlated with LT4 dose, while a diagnosis of differentiated thyroid cancer was positively correlated with LT4 dose. Formulation type was not a significant predictor.

CONCLUSION

In patients with post-surgical hypothyroidism, L-EF-LT4 demonstrated equivalent therapeutic efficacy to T-LT4 in terms of dose requirement and TSH control. These findings support the use of L-EF-LT4 as a viable alternative to tablet LT4, particularly in clinical scenarios where flexible timing of ingestion may improve patient compliance.