THU664 Discontinuation Of Low-dose Levothyroxine Therapy For Patients With Subclinical Hypothyroidism Is Feasible: A Pilot, Randomized, Double-blind, Placebo-controlled Trial

Disclosure: S. Maraka: None. R. Owen: None. N.M. Singh Ospina: None. M. Knox: None. T. Dodds: None. H. Spencer: None. A. Albashaireh: None. A. Shah: None. S. Syed: None. S. Naqvi: None. H. Motahari: None. S. Thumma: None. E. Ambrogini: None. J.P. Brito: None. Objective: Levothyroxine (LT4) therapy has not been shown to improve quality of life (QoL), thyroid-related symptoms, cardiovascular events, or mortality for patients with subclinical hypothyroidism (SCH) in clinical trials. We conducted this pilot, double-blind, placebo-controlled clinical trial to evaluate the effects of LT4 discontinuation among adults with SCH. Methods: We aimed to randomize 50 adults 1:1 to continue receiving LT4 (25-75 mcg/day) for SCH or discontinue it (switch to placebo). The primary outcome was feasibility. Secondary outcomes included changes in QoL measures (Thyroid-specific QoL Patient-Reported Outcome [ThyPRO]-Hypothyroid Symptoms and Tiredness scores, EuroQoL 5-Dimension Self-Report Questionnaire [EQ-5D]) assessed at baseline and 6 months post-randomization, and incidence of adverse events (overt hypothyroidism, hyperthyroidism, atrial fibrillation, stroke, acute coronary syndrome, heart failure, fracture, mortality). Higher scores for ThyPRO indicate more symptoms and tiredness and for EQ-5D, better health state. Data are reported as mean (standard deviation). Analysis of covariance model adjusting for age and baseline measure of the variable was performed for the outcomes based on the intention-to-treat principle. Results: Fifty participants were enrolled (33% recruitment rate); 24 were randomized to the LT4 and 26 to the discontinuation group. Five patients were excluded post-randomization due to lack of ascertainment of SCH diagnosis (final N=45; 21 LT4, 24 discontinuation). There was no statistically significant difference at baseline between the discontinuation and LT4 groups in age [65.7 (10.6) vs. 71.0 (7.9) yrs], gender (male 75 vs. 86%), LT4 dose (25 mcg; 29.2 vs. 33.3%, 50 mcg; 54.2 vs. 47.6%, 75 mcg; 16.7 vs. 19.0%), TSH [3.1 (1.0) vs. 3.2 (1.4) mIU/L], TPOAb positivity (17 vs. 19%), ThyPRO-Hypothyroid Symptoms [27.1 (20.4) vs. 21.1 (18.4)] and Tiredness score [33.2 (23.7) vs. 31.1 (23.9)], and EQ-5D [0.746 (0.229) vs. 0.758 (0.193)]. A patient in the discontinuation group withdrew for personal reasons (98% completion rate). Two patients in the discontinuation group met study criteria to restart LT4 (TSH>10 mIU/L; n=1, fatigue; n=1). At final visit, 34.8% of patients in the discontinuation group had mild SCH compared to 9.5% of patients on LT4 (p=0.07). There was no statistically significant difference between the discontinuation and LT4 groups in ThyPRO-Hypothyroid Symptoms [28.3 (22.8) vs. 22.9 (19.5)], Tiredness [27.6 (22.8) vs. 32.8 (22.1)], and EQ-5D score [0.750 (0.232) vs. 0.741 (0.180)]. A patient suffered rib fracture (placebo); no other adverse event of interest was reported. Conclusion: This pilot clinical trial showed the feasibility and safety of discontinuing LT4 in patients with SCH. These findings support proceeding with a larger multi-site clinical trial to fully assess the effects of LT4 discontinuation. Presentation: Thursday, June 15, 2023