The circadian rhythms of serum prolactin in nurses working on a night shift

The diurnal rhythm of serum prolactin levels was investigated in five night-workers (night nurses). Maximal values were found during the day time sleep period. Besides this shift from night to day time, disturbances of the secretion pattern (i.e., 2 prolactin peaks, increased differences between maximal and minimal values) were observed in most cases. The abnormal prolactin rhythm remained constant throughout the night shift period in all but one case.