The effects of Islamic fasting on the thyroid function in young adults

Previous studies have reported different results in the serum levels of T3 and T4 in people fasting. We investigated the effects of Ramadan fasting on serum levels of T3, T4, T3RU, TSH, FT3, and FT4.

This study was a quasi-experimental study performed on 52 male and 46 female healthy volunteers who fasted at least 25 days during Ramadan, 11.5±0.5 hours each day. Blood sampling was done in three sessions: one week before and on days 14th and 28th of Ramadan.

Both total T3 and free T4 levels decreased significantly. Mean FT3 level decreased from 153.5±25.7 ng/dL before Ramadan to 129.1±22.7 ng/dL on 28th of Ramadan (p<0.001), and T4 decreased from 8.5±1.5 μg/dL to 7.5±1.3 μg/dL in the same period (p<0.001). FT3 levels showed an initial increase by day 14 with subsequent return to the previous levels (p<0.001). FT4 levels decreased significantly only in male subjects (1.3±0.4 μg/dL to 1.2±0.3 μg/dL. P=0.01). There was no significant change in the level of T3RU. Finally, a mild decrease was observed in TSH levels.

All changes were within normal limits.