Liquid formulations of Levothyroxine with ethanol or with parabens for treatment of congenital hypothyroidism: similar TSH and fT4 values in the first 6 months of follow up.

Abstract

Purpose: Two liquid formulations of Levothyroxine (L-T4) are available in Italy: one containing ethanol and one containing parabens. In the literature, few data demonstrate efficacy of the ethanol-free formulation. Our study aims at comparing the efficacy of these formulations in the first six months of treatment in newborns affected by congenital hypothyroidism (CH).

Methods: 236 children diagnosed with CH in our centre between 2011 and 2022 were enrolled according to the L-T4 formulation used: ethanol-containing (group A) or parabens-containing (group B). We collected data at diagnosis (gestational age, TSH, fT4, daily dose/kg, aetiology), at 7-15 days, 1 month, 3 months, and 6 months after diagnosis (TSH, fT4, daily dose/kg).

Results: 164 patients were enrolled in group A and 72 in group B. TSH was lower in group B compared to group A at diagnosis. fT4 was significantly higher in group B at 1 and 3 months, but always in the correct range for age. L-T4 dosage was lower in group B than in group A at 7-15 days, 1 month, and 6 months after diagnosis. Since more patients had gland in situ in group B than in group A (75 vs 57%), we repeated the previous analyses in this subgroup of patients, confirming the results. In both subgroups, the percentages of patients with TSH and fT4 concentrations within normal range during follow-up were not significantly different.

Conclusion: Our study confirms the efficacy of both therapeutic strategies in the treatment of CH, allowing to individualize therapy depending on the needs of each patient.