Shift work and circadian dysregulation of reproduction

Gamble, K.L., Resuehr, D., and Johnson, C.H. (2013). Shift work and circadian dysregulation of reproduction. Front Endocrinol, 4:92.

Health impairments, including reproductive issues, are associated with working nights or rotating shifts. For example, shift work has been associated with an increased risk of irregular menstrual cycles, endometriosis, infertility, miscarriage, low birth weight or pre-term delivery, and reduced incidence of breastfeeding. Based on what is known aboutcircadianregulation of endocrine rhythms in rodents (and much less in humans), thecircadianclock is an integral regulatory part of the reproductive system. When this 24-h program is disordered by environmental perturbation (such as shift work) or genetic alterations, the endocrine system can be impaired.

The purpose of this review is to explore the hypothesis that misalignment of reproductive hormones with the environmental light-dark cycle and/or sleep-wake rhythms can disrupt menstrual cycles, pregnancy, and parturition. We highlight the role of thecircadianclock in regulating human reproductive physiology and shift work-induced pathology within each step of the reproductive axis while exploring potential mechanisms from the animal model literature. In addition to documenting the reproductive hazards of shift work, we also point out important gaps in our knowledge as critical areas for future investigation.

Shift work affects ~15% of the workforce in America. Circadian regulation of endocrine factors affects reproduction and hormone release. These hormones can greatly impact mood as well as fertility and emotional strain associated with infertility issues. Awareness of environmental hazards such as shift work may have implications for these patients.