Effect of Ramadan Fasting on Thyroid Hormone Levels in Patients on Levothyroxine Treatment.

OBJECTIVE To evaluate the changes in thyroid functions in Ramadan, and compare late evening and pre-seheri use of levothyroxine in patients with hypothyroidism. STUDY DESIGN Cross-sectional study. PLACE AND DURATION OF STUDY Department of Endocrinology, Ankara Ataturk Education and Research Hospital and Ankara Yildirim Beyazit University, Turkey, from May to June 2018. METHODOLOGY Patients who were on levothyroxine treatment and having normal thyroid functions were recruited for the study in the last one week before Ramadan. Patients were offered to take levothyroxine at 22.30-23.00 pm before sleep or between 01:30-03:00 am at least 30 min pre-seheri. RESULTS There were 53 (85.5%) female and 9 (14.5%) male patients. Basal thyrotrophin (TSH) was 2.02 μIU/mL (0.27-4.14) and insignificantly increased at the end of Ramadan [2.18 μIU/mL (0.04-19.69), p=0.167]. Free-triiodothyronine (fT3) decreased while free-thyroxine (fT4) increased (p<0.001 for both). Eighteen patients preferred to take levothyroxine in late evening and 44 preferred to take at pre-seheri. There were insignificant increases in TSH in both groups (p=0.401 and p=0.276, respectively). At the end of Ramadan, TSH increased in 39 (63.9%), decreased in 22 (36.1%), and did not change in one patient. CONCLUSION Increase in TSH was not significant after Ramadan. While there was an insignificant increase in median TSH, about one-third of patients had lower TSH, indicating for the need to evaluate every patient individually and follow closely during Ramadan. Clinical studies with larger sample sizes will be helpful to determine the optimal time for levothyroxine use during Ramadan. Key Words: Thyroid functions, Ramadan fasting, Hypothyroidism, Levotyhroxine.