SAT-443 Impact of Fasting on Plasma Thyrotropin in Hypothyroid Patients Taking Levothyroxine During Ramadan (IFT-R Study)

Background and Aim: We previously showed in a retrospective analysis that the plasma TSH rises significantly post-Ramadan in levothyroxine-treated hypothyroid patients, possibly as a result of changes in the eating habit during the non-fasting period from dusk until dawn. The aim of this study is to determine the best time for taking levothyroxine during Ramadan in order to minimize changes in thyroid function tests. Methods: in a randomized prospective design, hypothyroid patients taking levothyroxine for greater than 6-months were randomized to take levothyroxine at one of the following 3 times during Ramadan: (group 1) at dusk after a prolonged fast and 30-minutes before the Iftar meal, (group 2) ≥ 3-hours after the Iftar meal, or (group 3) at dawn 30-minutes before Suhur meal. Patients were instructed to allow a minimum of 3-hours between the last meal and levothyroxine and to refrain from eating and drinking for at least 30-minutes after taking levothyroxine. Thyroid function tests were performed within 3-months before Ramadan and within 6-weeks post Ramadan. To estimate intent-to-treat effects, we examined pre- and post-Ramadan thyroid function tests in relation to the assigned levothyroxine administration times. Results: 147 patients were randomized into the study and the respective number of patients in groups 1, 2 and 3 were 50, 46 and 51. The mean age of participants was 43.5±12.4 years [range 21.0-86.0] and 78% were females with no statistical differences in the mean age or gender distribution between the 3 groups. The respective pre-Ramadan mean TSH values for the 3 groups were 2.49 mIU/L, 2.16 mIU/L and 3.37 mIU/L with no significant differences at baseline. Post-Ramadan mean TSH values were 2.47 mIU/L, 4.26 mIU/L and 3.85 mIU/L for groups 1, 2 and 3 respectively. The pre- and post-Ramadan mean TSH differences were significant only for group 2, who took levothyroxine 3-hours post-Iftar (P-value 0.041). There were no significant differences in the free-T4 levels across the 3-groups before and after Ramadan. In a subset of 85 patients, the preferred times for levothyroxine administration during Ramadan were 44.7% before Iftar, 50.6% post-Iftar and only 4.7% were in favor of taking the medication before Suhur meal. Conclusions: Levothyroxine-treated hypothyroid patients who took levothyroxine 3-hours after the main Iftar meal showed a significant increase in plasma TSH post-Ramadan, possibly reflecting a reduced time period between levothyroxine administration and the previous meal. There was no significant change in the mean plasma TSH for patients taking levothyroxine at dusk before Iftar or at dawn before Suhur. The least patient-preferred time for taking levothyroxine was at dawn before Suhur possibly due to time constraints before the start of fasting.