title: Relationship between thyroid stimulating hormone and night shift work.
abstract: BACKGROUND
  Night shift work has well-known adverse effects on health. However, few studies have investigated the relationship between thyroid diseases and night shift work. This study aimed to examine night shift workers and their changes in thyroid stimulating hormones (TSH) levels over time.
  
  
  METHODS
  Medical check-up data (2011-2015) were obtained from 967 female workers at a university hospital in Incheon, Korea. Data regarding TSH levels were extracted from the records, and 2015 was used as a reference point to determine night shift work status. The relationships between TSH levels and night shift work in each year were analyzed using the general linear model (GLM). The generalized estimating equation (GEE) was used to evaluate the repeated measurements over the 5-year period.
  
  
  RESULTS
  The GEE analysis revealed that from 2011 to 2015, night shift workers had TSH levels that were 0.303 mIU/L higher than the levels of non-night shift workers (95 % CI: 0.087-0.519 mIU/L,p= 0.006) after adjusting for age and department. When we used TSH levels of 4.5 ≥ mIU/L to identify subclinical hypothyroidism, night shift workers exhibited a 1.399 fold higher risk of subclinical hypothyroidism (95 % CI: 1.050-1.863,p= 0.022), compared to their non-night shift counterparts.
  
  
  CONCLUSIONS
  This result of this study suggests that night shift workers may have an increased risk of thyroid diseases, compared to non-night shift workers.
authors.affiliation: Department of Occupational and Environmental Medicine, Inha University Hospital, Incheon, Republic of Korea ; Department of Social and Preventive Medicine, School of Medicine, Inha University, Incheon, Republic of Korea.
authors.forename: So-Hyun
authors.initials: SH
authors.lastname: Moon
authors.affiliation: Department of Occupational and Environmental Medicine, Inha University Hospital, Incheon, Republic of Korea.
authors.forename: Bum-Joon
authors.initials: BJ
authors.lastname: Lee
authors.affiliation: Department of Occupational and Environmental Medicine, Inha University Hospital, Incheon, Republic of Korea ; Department of Social and Preventive Medicine, School of Medicine, Inha University, Incheon, Republic of Korea.
authors.forename: Seong-Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Department of Occupational and Environmental Medicine, Inha University Hospital, Incheon, Republic of Korea ; Department of Occupational and Environmental Medicine, School of Medicine, Inha University, Incheon, Republic of Korea.
authors.forename: Hwan-Cheol
authors.identifier: 0000-0002-3635-1297
authors.initials: HC
authors.lastname: Kim
keywords: Night shift; Subclinical hypothyroidism; Thyroid stimulating hormone