MON-LB102 Liquid L-Thyroxine Can Maintain Stable TSH Values in Patients with Hypothyroidism: A Prospective Study

In patients treated for hypothyroidism, the usual practice is to monitor TSH values yearly once a therapeutic dosage of levothyroxine (L-T4) is determined. No consistent data are present in literature about the stability of TSH levels in patients (without malabsorption) treated with liquid L-T4, in comparison to tablet L-T4. The aim of this study is to compare the stability of TSH in patients treated with liquid L-T4 formulation, with respect to those treated with tablet L-T4. Five hundred-twelve hypothyroid patients (without malabsorption or drug interference) with normal TSH at the basal evaluation while in treatment with liquid L-T4, were followed for 2 years. TSH, FT3, FT4 were re-evaluated after 1, and 2 years. For comparison, 206 hypothyroid patients (matched by age and gender) with normal TSH at the basal evaluation while in treatment with tablet L-T4 were followed for 2 years; TSH, FT3, FT4 were re-evaluated after 1, and 2 years. Gender, age, body mass index, history of chronic autoimmune thyroiditis, initial TSH level, and levothyroxine dose were analyzed for time to first abnormal TSH value. Age, gender, history of chronic autoimmune thyroiditis, body mass index, and levothyroxine dose, at the time of initial normal TSH were not associated significantly with time to abnormal TSH value. At 1 year, 92% of the patients receiving L-T4 liquid formulation continued to have a normal TSH, whereas only 84% of patients receiving tablet L-T4 did. At 2 years, 86% of patients receiving L-T4 liquid formulation continued to have a normal TSH, whereas only 75% of patients receiving tablet L-T4 had normal TSH values (p<0.05). In conclusion, these data suggest that liquid L-T4 can maintain normal TSH values in hypothyroid patients in the long term follow-up, more efficiently than tablet L-T4. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.