Increased and mistimed sex hormone production in night shift workers
Menée en Espagne à partir d'échantillons d'urine prélevés sur 75 salariés travaillant de nuit et sur 42 salariés travaillant de jour, cette étude met en évidence une production plus élevée d'hormones sexuelles et de mélatonine chez les travailleurs nocturnes, ce qui permettrait de rendre compte de l'association entre travail de nuit et risque de cancers liés aux hormones (sein et prostate)
Background:Night shift work has been associated with an increased risk for breast and prostate cancer. The effect of circadian disruption on sex steroid production is a possible underlying mechanism, underinvestigated in humans. We have assessed daily rhythms of sex hormones and melatonin in night and day shift workers of both sexes. Methods: We recruited 75 night and 42 day workers, aged 22-64 years, in different working settings. Participants collected urine samples from all voids over 24 hours on a working day. Urinary concentrations of 16 sex steroid hormones and metabolites (estrogens, progestagens and androgens) and 6-sulfatoxymelatonin were measured in all samples. Mean levels and peak time of total and individual metabolite production were compared between night and day workers. Results: Night workers had higher levels of total progestagens (geometric mean ratio (GMR) 1.65; 95% confidence interval (CI) 1.17, 2.32) and androgens (GMR: 1.44; 95% CI 1.03, 2.00), compared to day workers, after adjusting for potential confounders. The increased sex hormone levels among night shift workers were not related to the observed suppression of 6-sulfatoxymelatonin. Peak time of androgens was significantly later among night workers, compared to day workers (testosterone: 12:14 h; 10:06, 14:48 vs 08:35 h; 06:52, 10:46). Conclusions: We found increased levels of progestagens and androgens as well as delayed peak androgen production in night shift workers, compared to day workers. Impact: The increase and mistiming of sex hormone production may explain part of the increased risk for hormone-related cancers observed in night shift workers.