The Effects of Nocturnal Life on the Circadian Patterns of Sex Hormones in Young Healthy Men

Abstract

Irregular meals (mainly the skipping of breakfast) and inadequate sleep has become prevalent in young people. However, there has been inadequate attention on the adverse effects of this nocturnal life. We observed the 24-hr patterns of sex hormones and other relative hormones in ten medical students, with the randomized cross-over design, on either a diurnal life or a nocturnal life. The subjects on a diurnal life ate three meals (07:00, 13:00 and 19:00) and slept from 22:30 to 06:30. Nocturnal life was designed by skipping their breakfast but consuming a lot (> 50% of their daily food intake) in the evening and at night, sleeping from 01:30 to 08:30 the next morning. After three weeks in the experimental life, the 24-hr plasma concentrations of testosterone, free testosterone, dihydrotestosterone (DHT), androstenedione, prolactin, estrone, luteinizing hormone, cortisol and sex hormone binding globulin (SHBG) were measured every three hours. Plasma free testosterone and prolactin decreased, but cortisol increased when subjects followed the nocturnal life. In the diurnal lifestyle group, circadian rhythms were observed in the androgens (testosterone, free testosterone, DHT, androstenedione), prolactin, cortisol and SHBG in the cosinor analysis; however, circadian rhythms were almost extinguished in the nocturnal lifestyle group. Since sex hormones play important roles in the normal physiological condition, the effects of these changes in hormone concentration and its circadian rhythm should be considered and studied intensively.