Endocrine Abstracts

Background: Ramadan is the religious month in which Muslims fast from pre-dawn (suhoor) until sunset (iftar), abstaining from all kinds of food, and liquid. The major change in meal times may be challenging for hypothyroid patients on levothyroxine because levothyroxine has a narrow therapeutic index and should be taken on an empty stomach.

Objective: We aim to compare pre- and post-Ramadan Thyroid function tests of hypothyroid patients taking levothyroxine and to determine the best timing of levothyroxine intake during Ramadan.

Methods: We searched PubMed, Scopus, WOS, Google Scholar, Ovid, Science Direct, Clinical trials.gov, and Cochrane Library for studies published in English investigating the effect of Ramadan fasting on thyroid functions in hypothyroid patients on levothyroxine, and/or comparing different time points of the drug intake. Assessed outcomes were TSH change, Free T4 change, number of patients above reference range of TSH. Subgroups of different time points (Pre-Iftar, Post-Iftar, and Pre-Suhoor) were analyzed separately. The analysis was done by RevMan software. The National Institutes of Health (NIH) quality assessment tools were used according to the study designs.

Results: Twelve studies; 3 RCTs, and 9 observational studies were eligible. All studies compared the same group before and after Ramadan (pre-post study). Ramadan fasting is associated with a statistically significant increase in TSH (MD= -1.07, CI 95% [-1.46, -0.67], P< 0.00001). However, no difference was found as regards the number of patients with TSH above the reference range (RR= 0.66, [0.41, 1.08], P= 0.1). Also, It didn’t reflect on an increase in FT4 (MD= 0.01, [-0.03, 0.06], P= 0.59). Our analysis showed that taking the drug at pre-iftar, or post-iftar significantly increases TSH after Ramadan (P= 0.009, and 0.01 respectively). Taking the drug before suhoor (0.5 to 1 hour) showed no significant difference (MD= -0.72, [-2.25, 0.81], P= 0.36), but the heterogeneity between the studies makes the significance inconclusive.

Conclusion: TSH increases significantly after Ramadan. Choosing an optimal timing is still a challenge, but our analysis suggests that taking the drug before suhoor meal by one hour is the best option. More high quality research is warranted to break this controversy.