Ramadan fasting alters endocrine and neuroendocrine circadian patterns. Meal-time as a synchronizer in humans?

Muslims must refrain from eating, drinking, smoking, and sexual relations f rom sunrise to sunset during the month of Ramadan. Serum concentrations of melatonin, steroid hormones (cortisol, testosterone), pituitary hormones (p rolactin, LH, FSH, GH, TSH) and thyroid hormones (free thyroxin and free tr iiodothyronine) were documented around the clock at six 4-hourly intervals before Ramadan began and on the twenty-third day of Ramadan (daytime fastin g). Time series were analysed with repeated measures ANOVA. Statistically s ignificant differences were found in some variables: the nocturnal peak of melatonin was diminished and may have been delayed; there was a shift in th e onset of cortisol and testosterone secretion; the evening peak of prolact in was enhanced, FSH and GH rhythmic patterns were affected little or not a t all by Ramadan fasting and only the serum TSH rhythm was blunted over the test time span. These data show that daytime fasting, modifications in sle ep schedule and psychological and social habits during Ramadan induce chang es in the rhythmic pattern of a number of hormonal variables. (C) 2001 Else vier Science Inc. All rights reserved.