Increased and mistimed sex hormone production in night shift workers.
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, ages 22 to 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 intervals (CI), 1.17-2.32] and androgens (GMR: 1.44; 95% CI, 1.03-2.00), compared with 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 with day workers (testosterone: 12:14 hours; 10:06-14:48 vs. 08:35 hours; 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 with day workers.


CONCLUSIONS
The increase and mistiming of sex hormone production may explain part of the increased risk for hormone-related cancers observed in night shift workers.
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain. IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Spain. CIBER Epidemiología y Salud Pública (CIBERESP), Madrid, Spain. kpapantoniou@creal.cat.
Kyriaki
K
Papantoniou
IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain.
Oscar J
OJ
Pozo
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain. IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Spain. CIBER Epidemiología y Salud Pública (CIBERESP), Madrid, Spain.
Ana
A
Espinosa
IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Spain.
Josep
J
Marcos
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain. IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Spain. CIBER Epidemiología y Salud Pública (CIBERESP), Madrid, Spain.
Gemma
G
Castaño-Vinyals
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain. IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Spain. CIBER Epidemiología y Salud Pública (CIBERESP), Madrid, Spain.
Xavier
X
Basagaña
Deparatment d'Empresa i Ocupació de la Generalitat de Catalunya, Barcelona, Spain.
Elena
E
Juanola Pagès
Occupational Health Service, Parc de Salut Mar, Barcelona, Spain. CISAL-Centre for Research in Occupational Health, University Pompeu Fabra, Barcelona, Spain.
Joan
J
Mirabent
Ferrocarrils de la Generalitat de Catalunya, Barcelona, Spain.
Jordi
J
Martín
SEAT, S.A., Barcelona, Spain.
Patricia
P
Such Faro
Hospital de Viladecans, Barcelona, Spain.
Amparo
A
Gascó Aparici
Chronobiology, University of Surrey, Guildford, United Kingdom.
Benita
B
Middleton
Chronobiology, University of Surrey, Guildford, United Kingdom.
Debra J
DJ
Skene
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain. IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Spain. CIBER Epidemiología y Salud Pública (CIBERESP), Madrid, Spain. National School of Public Health, Athens, Greece.
Manolis
M
Kogevinas
D000328:Adult; D000728:Androgens / Q000652:urine*; D001943:Breast Neoplasms / Q000453:epidemiology / Q000652:urine; D002940:Circadian Rhythm / Q000502:physiology*; D004967:Estrogens / Q000652:urine*; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives / Q000652:urine; D008875:Middle Aged; D011372:Progestins / Q000652:urine*; D011471:Prostatic Neoplasms / Q000453:epidemiology / Q000652:urine; D014940:Work Schedule Tolerance / Q000502:physiology*; D055815:Young Adult
D000728:Androgens; D004967:Estrogens; D011372:Progestins; C054513:6-sulfatoxymelatonin; D008550:Melatonin