Predawn Versus Preiftar Timing of Levothyroxine Administration During Ramadan Intermittent Fasting: A Multicenter Randomized Controlled Trial

OBJECTIVES: To compare 2 levothyroxine (LT4) dosing regimens during Ramadan: preiftar and predawn, with respect to thyroid biochemical control and patient satisfaction. METHODS: This multicenter, open-label randomized controlled trial recruited adults with primary hypothyroidism from 3 Saudi cities (Jeddah, Riyadh, and Al-Ahsa). Patients with thyroid cancer were excluded. Thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels were measured 2 weeks before and 4 to 6 weeks after Ramadan. Participants were randomized to take LT4 either before breaking the fast (preiftar) or just before fasting began (predawn). RESULTS: A total of 303 (156 preiftar and 147 predawn) participants completed the study. Groups were comparable in demographic characteristics and comorbidities. Mean age was 49 ± 12 years; 87% were female; mean disease duration was 9.7 ± 8.3 years. Weekly LT4 dose was 753 ± 349 μg (preiftar) versus 733 ± 266 μg (predawn; P = .001). Pre-Ramadan TSH level was 2.56 ± 2.16 mIU/L versus 2.46 ± 1.72 mIU/L (P = .3), and FT4 level was 13.45 ± 2.1 versus 13.08 ± 2.4 pmol/L (P = .16). Post-Ramadan TSH level was 3.64 ± 4.1 versus 4.07 ± 4.2 mIU/L (P = .78), and FT4 level was 12.96 ± 0.1 versus 12.64 ± 0.2 pmol/L (P = .003). Within-group post-Ramadan changes were nonsignificant. Repeated measures analysis of variance showed no significant differences in TSH or FT4 levels over time or between groups (P = .47 and P = .81). Compliance and satisfaction were comparable. CONCLUSION: Both preiftar and predawn LT4 regimens maintained thyroid stability during Ramadan. Either can be safely adopted according to patient preference.