Circadian rhythm deregulation and thyroid dysfunction: results of an observational study on night shift workers

Context. It has been decades since the circadian variation of the secretion of the thyroid stimulating hormone (TSH) was proven in humans. Even so, there are few studies on human beings that explored the relationship existing between night shift circadian rhythm deregulation and thyroid disorders. Methods. We have revised the occupational medicine files of all employees in a single speciality hospital to conduct an observational study on the prevalence of thyroid disorders in night shift compared to day shift workers. Age, gender, occupational history, body mass index and specialist diagnosed thyroid disorders were recorded. Numerical variables were compared with ANOVA test, and categorical ones with chi test (StatPlus for Mac version v6). Results. Obesity was slightly more prevalent in night shift workers, but not statistically significant. Instead, we found a significant increase in the prevalence of thyroid disorders in night shift workers (X= 7.424, p = 0.006). As this is a mere observational study, our results only contribute to the pool of data concerning the relationship between thyroid dysfunction and night shifts. Conclusions: These results should raise awareness, particularly among occupational physicians and endocrinologists, about the influence of sleep and circadian rhythm deregulation on the raising incidence of thyroid disorders.