Endocrine Abstracts

Background: Sleep loss in the early morning has been shown to reduce secretory activity of the pituitary–gonadal axis in men, but the determinants of this effect are unknown.

Objective: To assess the effects of sleep restriction on serum concentrations of LH, testosterone , and prolactin (PRL).

Methods: Fifteen young, healthy men were examined in a condition of sleep time restriction to 0245–0700 h for two consecutive nights and in a control condition of regular sleep (2245–0700 h). After the second night, serum concentrations of LH, testosterone, and PRL were monitored over a 15 h period. In addition, these hormones were measured in serum samples obtained in eight healthy men in the morning after one night of total sleep deprivation, of 4.5 h sleep (2230–0300 h), and of regular 7 h sleep.

Results: Serum LH, testosterone, and PRL concentrations showed characteristic diurnal variations across the 15-h period without any differences between the 4 and 8 h sleep conditions. However, total sleep deprivation and 4.5 h of sleep restricted to the first night-half markedly decreased morning testosterone and PRL concentrations (both P≤0.05).

Conclusion: Collectively, our data indicate that the effect of sleep restriction on pituitary-gonadal secretory activity depends on the timing of sleep restriction. While sleep loss in the early part of the night does not affect testosterone and PRL, early awakening and wakefulness during the second part of the night profoundly reduce circulating testosterone and PRL.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.