Korean J Fam Pract 2020; 10(1): 3-8  https://doi.org/10.21215/kjfp.2020.10.1.3
Relationship between Shift Work and Subclinical Hypothyroidism
Hye-a Hwang, Young-jee Jeon*
Department of Family Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea
Young-jee Jeon
Tel: +82-52-250-8847, Fax: +82-52-250-8330
E-mail: yjjeon@uuh.ulsan.kr
ORCID: http://orcid.org/0000-0002-8070-2453
Received: October 1, 2019; Revised: December 19, 2019; Accepted: December 19, 2019; Published online: February 20, 2020.
© The Korean Academy of Family Medicine. All rights reserved.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: To date, only a few studies have reported the relationship between shift work and subclinical hypothyroidism. Therefore, this study aimed to investigate this relationship. Subclinical hypothyroidism is defined as normal thyroxine (free T4) and thyrotropin (thyroid stimulating hormone, TSH) levels above 10 mU/L.
Methods: This study included 12,126 male participants who visited Ulsan University Hospital health promotion center from March 1, 2016 to February 28, 2017. Participants answered a self-administered survey about their marital status, educational level, smoking habits, alcohol intake, and frequency of physical activity. Venous blood sampling was performed after maintaining fasting state for at least 8 hours to test for fasting glucose, hemoglobin A1c, total cholesterol, TSH, and free T4.
Results: The TSH level was significantly higher in shift workers than that in the non-shift workers, whereas free T4 level did not show any difference between the two groups. In the shift work group, the odds ratio for subclinical hypothyroidism was significantly higher (odds ratio, 1.99, 95%; confidence interval, 1.16–3.40). This result persisted after adjusting for covariates of age, body mass index, educational level, smoking habits, alcohol intake, and frequency of physical activity.
Conclusion: The odds of subclinical hypothyroidism were higher in the shift work group. Therefore, clinicians should pay more attention to detect subclinical hypothyroidism in shift workers.
Keywords: Shift Work Schedule; Occupational Groups; Thyroid Disease; Hypothyroidism
  1. Costa G. Shift work and health: current problems and preventive actions. Saf Health Work 2010; 1: 112-23.
    Pubmed KoreaMed CrossRef
  2. Abu Farha R, Alefishat E. Shift work and the risk of cardiovascular diseases and metabolic syndrome among Jordanian employees. Oman Med J 2018;33: 235-42.
    Pubmed KoreaMed CrossRef
  3. Brum MC, Filho FF, Schnorr CC, Bottega GB, Rodrigues TC. Shift work and its association with metabolic disorders. Diabetol Metab Syndr 2015; 7:45.
    Pubmed KoreaMed CrossRef
  4. Brudnowska J, Pepłońska B. [Night shift work and cancer risk: a literature review]. Med Pr 2011; 62: 323-38. Polish.
  5. Papantoniou K, Devore EE, Massa J, Strohmaier S, Vetter C, Yang L, et al. Rotating night shift work and colorectal cancer risk in the nurses' health studies. Int J Cancer 2018; 143: 2709-17.
    Pubmed KoreaMed CrossRef
  6. Asranna A, Taneja RS, Kulshreshta B. Dyslipidemia in subclinical hypothyroidism and the effect of thyroxine on lipid profile. Indian J Endocrinol Metab 2012; 16(Suppl 2): S347-9.
    Pubmed KoreaMed CrossRef
  7. Nyrnes A, Jorde R, Sundsfjord J. Serum TSH is positively associated with BMI. Int J Obes (Lond) 2006; 30: 100-5.
    Pubmed CrossRef
  8. Kadiyala R, Peter R, Okosieme OE. Thyroid dysfunction in patients with diabetes:clinical implications and screening strategies. Int J Clin Pract 2010;64: 1130-9.
    Pubmed CrossRef
  9. Hak AE, Pols HA, Visser TJ, Drexhage HA, Hofman A, Witteman JC. Subclinical hypothyroidism is an independent risk factor for atherosclerosis and myocardial infarction in elderly women: the Rotterdam Study. Ann Intern Med 2000; 132: 270-8.
    Pubmed CrossRef
  10. Owen PJ, Rajiv C, Vinereanu D, Mathew T, Fraser AG, Lazarus JH. Subclinical hypothyroidism, arterial stiffness, and myocardial reserve. J Clin Endocrinol Metab 2006; 91: 2126-32.
    Pubmed CrossRef
  11. Biondi B, Fazio S, Palmieri EA, Carella C, Panza N, Cittadini A, et al. Left ventricular diastolic dysfunction in patients with subclinical hypothyroidism. J Clin Endocrinol Metab 1999; 84: 2064-7.
    Pubmed CrossRef
  12. Biondi B. Mechanisms in endocrinology: heart failure and thyroid dysfunction. Eur J Endocrinol 2012; 167: 609-18.
    Pubmed CrossRef
  13. McDermott MT, Ridgway EC. Subclinical hypothyroidism is mild thyroid failure and should be treated. J Clin Endocrinol Metab 2001; 86: 4585-90.
    Pubmed CrossRef
  14. Fatourechi V. Subclinical hypothyroidism: an update for primary care physicians. Mayo Clin Proc 2009; 84: 65-71.
    Pubmed KoreaMed CrossRef
  15. Moon SH, Lee BJ, Kim SJ, Kim HC. Relationship between thyroid stimulating hormone and night shift work. Ann Occup Environ Med 2016; 28: 53.
    Pubmed KoreaMed CrossRef
  16. Cho YW. Clinical implication of serum TSH concentration. J Korean Endocr Soc 2007; 22: 87-94.
  17. Lewandowski K. Reference ranges for TSH and thyroid hormones. Thyroid Res 2015; 8(Suppl 1): A17.
    KoreaMed CrossRef
  18. Shavali SS, Haldar C. Effects of continuous light, continuous darkness and pinealectomy on pineal-thyroid-gonadal axis of the female Indian palm squirrel, Funambulus pennanti. J Neural Transm (Vienna) 1998; 105: 407-13.
    Pubmed CrossRef
  19. Goichot B, Weibel L, Chapotot F, Gronfier C, Piquard F, Brandenberger G. Effect of the shift of the sleep-wake cycle on three robust endocrine markers of the circadian clock. Am J Physiol 1998; 275: E243-8.
    Pubmed CrossRef
  20. Lee H, Cho CH, Kim L. Human circadian rhythms. Sleep Med Psychophysiol 2014; 21: 51-60.
  21. Morin LP. Serotonin and the regulation of mammalian circadian rhythmicity. Ann Med 1999; 31: 12-33.
    Pubmed CrossRef
  22. Chan S, Debono M. Replication of cortisol circadian rhythm: new advances in hydrocortisone replacement therapy. Ther Adv Endocrinol Metab 2010;1: 129-38.
    Pubmed KoreaMed CrossRef
  23. Korshunov KS, Blakemore LJ, Trombley PQ. Dopamine: a modulator of circadian rhythms in the central nervous system. Front Cell Neurosci 2017; 11: 91.
    Pubmed KoreaMed CrossRef
  24. Magrini A, Pietroiusti A, Coppeta L, Babbucci A, Barnaba E, Papadia C, et al. Shift work and autoimmune thyroid disorders. Int J Immunopathol Pharmacol 2006; 19(4 Suppl): 31-6.

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