the effect of ramadan fasting on thyroid hormones in 9‐13 years old pre‐menarche girls

introduction: muslims fast from dawn to dusk during ramadan. the effects of prolonged food deprivation on endocrine hormones have been studied in healthy adults but no previous study has investigated this effect on children. this study aimed to evaluate the feasible changes in serum level of thyroxin (t3), tetraiodothyronin (t4), thyroid stimulating hormone (tsh) and body composition in pre-menarche girls. methods: this cohort study was performed through ramadan 2012. we enrolled fifty-eight 9-13years old girls (weight 34.20±7.96 kg, height 142.01±7.76 cm) in two groups from (31  and 27 in fasted and non-fasted groups, respectively) prior to ramadan until afterwards. weight and height of the subjects were measured using standard methods, and then body mass index (bmi) was calculated.  body composition was measured using bio impedance analyzer (bia) method.  serum concentrations of t3, t4 and tsh hormones were measured by radio immunoassay (ria). paired t-test was used to compare result of each group before and after ramadan. independent t-test was used to compare two groups together. tanner intervention variable was controlled by generalized linear models intervening test. spss.11 software was used for data analysis. results: ramadan fasting induces a significant decrease in bmi and weight on fasted group (p=0.005, p=0.044, respectively) while a significant increase was observed in non-fasted group (p<0.001). although, t3 decreased significantly by fasting (p<0.001), it remained in the normal range. hence, t4 decreased and tsh increased slightly in both groups. conclusions: according to our findings, despite a significant reduction of t3 in fasting group, variation in thyroid hormones level remained in the normal range during ramadan fasting.