Shift work is associated with higher risks of subclinical hypothyroidism and diabetes due to changes in circadian rhythm. Night shift work can increase TSH levels and the risk of subclinical hypothyroidism in women. It is also associated with higher risks of obesity, type 2 diabetes, and poorer glucose control, possibly because shift work promotes unhealthy eating behaviors and weight gain over time. Screening for thyroid disorders and managing weight are important for shift workers' health.

1. Managing Diabetes
And Thyroid Disease In the
Filipino Shift Worker
Nemencio A. Nicodemus Jr., MD, FPCP, FPSEDM
Professor, University of the Philippines-College of Medicine

2. What is Shift Work?
“A type of work schedule in which groups
of workers rotate through set periods throughout
the day, typically performing the same kind
of work”
“Work that takes place on a schedule outside the
traditional 9 am – 5 pm day.”
“Can involve evening or night shifts, early
morning shifts, and rotating shifts”
- Business Dictionary
- National Sleep Foundation

3. Why do we need shift work?
• Critical services on 24 hour basis
• Police, fire, military, healthcare, utilities,
transportation,
• A production process > 8 hours or continuous
• Expensive machinery that must be used
continuously to be profitable
• Support services for other shift workers
• Convenience

5. How does the body work?
• Internal Biological
Clock
• “Circadian
rhythm”
• Suprachiasmatic
nucleus
• External
Stimulants

6. External Stimulants: “Zeitgebers”

7. Zeitgebers affect food intake

8. FT3 shows a circadian rhythm with
a periodicity that lags behind TSH
Russel W, et al. J Clin Endocrinol Metab 93: 2300–2306, 2008

9. Females had significantly higher TSH
levels than males
Ehrenkranz J, et al. Thyroid. 2015 Aug;25(8):954-61

11. Shift Work and
Thyroid Diseases

12. Augmentation of the nocturnal
TSH rise with sleep deprivation
Pannain S & Cauter EV. Sleep Med Clin 2 (2007) 147–159

13. Night shift workers had TSH levels that
were 0.303 mIU/L higher than the levels
of non-night shift workers
Moon et al. Annals of Occupational and Environmental Medicine (2016) 28:53

14. Night shift workers exhibited a 1.399-fold
higher risk of subclinical hypothyroidism
Moon et al. Annals of Occupational and Environmental Medicine (2016) 28:53

15. Prevalence of Thyroid Disorders in
The Philippines, 2008
Thyroid Function Status Prevalence (%)
True Hyperthyroidism 0.61
Subclinical hyperthyroidism 5.33
True Hypothyroidism 0.41
Subclinical hypothyroidism 2.18
Normal 91.47
Rabocca JC, et al. for the PSEM PhilTiDes Working Group. JAFES; 27(1): 27-33, May 2012

16. Aziz M, et al. J Atheroscler Thromb, 2017; 24: 643-659
Total cholesterol, triglycerides and LDL were
higher in SCH as compared to EU: Meta-analysis
27.4 mg/dl
45.2 mg/dl
24.4 mg/dl
SCH: subclinical hypothyroidism; EU: euthyroid

17. Significantly higher CIMT values among subjects
with SCH as compared to those with EU:
Meta-Analysis
Aziz M, et al. J Atheroscler Thromb, 2017; 24: 643-659 SCH: subclinical hypothyroidism; EU: euthyroid

18. Subclinical hypothyroidism is associated with
an increased risk of CHD mortality:
Meta-Analysis of Prospective Cohort Studies
Sun J, et al. Int J Endocrinol. 2017; 2017: 8130796
* A total of 16 studies were included for meta-analysis

19. SCH Is Associated With Increased IHD And CV
Mortality Only In Younger Populations
Razvi S, et al. (J Clin Endocrinol Metab 93: 2998–3007, 2008
Middle aged
Older

20. Levothyroxine substitution yielded a mean reduction in
TC (A) and LDL (B): Meta-Analysis of RCTs
Li X, et al. Clinical Endocrinology. 2017;87:1–9
Twelve trials, with 940 participants

21. Treatment of SCH Reduces IHD and
All-Cause Mortality in Younger Patients
Razvi S, Weaver JU, Butler TJ, Pearce SH. Arch Intern Med. 2012;172:811-7
Fatal and nonfatal IHD events
All-cause mortality
Death due to circulatory diseases
Death due to IHD events
Death due to malignant neoplasms
Fatal and nonfatal CVA
Atrial fibrillation
Outcomes
Retrospective cohort study (database analysis)
Population treated, 1634; not treated,1459
Median follow-up of 7.6 y

22. SCH is a risk factor for miscarriage in women
before 20 weeks of pregnancy: Meta analysis
Zhang Y, Wang H, Pan X, Teng W, Shan Z (2017) Patients with subclinical hypothyroidism before 20 weeks of pregnancy have a higher risk of
miscarriage: A systematic review and meta-analysis. PLoS ONE 12(4): e0175708. https://doi.org/10.1371/journal.pone.0175708
Nine studies comparing the prevalence of miscarriage in pregnant women with SCH
with those who were euthyroid were selected

23. Approach to SCH in Pregnancy:
American Thyroid Association 2017
LT4 therapy is
recommended
TPOAb(+) with TSH greater than the pregnancy-specific
reference range
TPOAb(-) with a TSH >10.0 mU/L
LT4 therapy
MAY BE
considered
TPOAb(+) and (2.5 mU/L > TSH < UL of the pregnancy-specific
reference range)
TPOAb(-) and (pregnancy-specific reference range > TSH <
10.0 mU/L)
LT4 therapy is
NOT
recommended
TPOAb(-) with normal TSH (i.e. within the pregnancy-specific
reference range or < 4.0 mU/L if unavailable)
Alexander EK, et al. 2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease during
Pregnancy and the Postpartum. Thyroid, 1-162. DOI: 10.1089/thy.2016.0457

24. Timing of L-thyroxine Administration
• Levothyroxine
should be
consistently taken
either 60 minutes
before breakfast
OR
• at bedtime (3 or
more hours after the
evening meal)
Jonklaas, J., et al. Guidelines For The Treatment Of Hypothyroidism. 2014 THYROID, 24(12):1670-1751

25. Shift work
and Diabetes

27. Postprandial glycemic excursion is
higher during the night shift
Sharma A, et al. Diabetologia (2017) 60:1483–1490
White circles: Day shift
Black circles: Night shift

28. Time to peak
insulin and nadir
glucagon
suppression was
delayed during
night shift
Sharma A, et al. Diabetologia (2017) 60:1483–1490

29. ! cell responsivity to glucose and
disposition index were decreased
during the night shift
Sharma A, et al. Diabetologia (2017) 60:1483–1490
! cell responsivity Disposition index

30. Night shift work is associated
with higher type 2 diabetes odds
Vetter C, et al. Diabetes Care 2018;41:762–769

31. Rotating shiftwork including night shifts is
associated with higher type 2 diabetes odds
Vetter C, et al. Diabetes Care 2018;41:762–769

32. Duration of shift work was associated
with increased risk of type 2 diabetes
Duration of Rotating
Night Shift Work
Hazard ratio of
type 2 diabetes
Never 1.00
1–2 y 1.03 (0.98–1.08)
3–9 y 1.06 (1.00–1.11)
10–19 y 1.10 (1.02–1.18)
≥ 20 y 1.24 (1.13–1.37)
Adjusted for age, alcohol consumption, physical activity level, , smoking status, race,
menopausal status and hormone use, oral contraceptive use, family history of diabetes,
current aspirin use, quintiles of total calorie, diabetes dietary score, updated BMI category
Pan A, Schernhammer ES, Sun Q, Hu FB (2011. PLoS Med 8(12): e1001141. doi:10.1371/journal.pmed.1001141

33. Increased risk of type 2 diabetes in women
partly mediated through body weight
Pan A, Schernhammer ES, Sun Q, Hu FB (2011. PLoS Med 8(12): e1001141. doi:10.1371/journal.pmed.1001141

34. Shiftwork is associated with obesity,
despite higher levels of physical activity
Wyse CA, et al. (2017) Annals of Medicine, 49:5, 411-420

35. Links
between
shift work
and type 2
diabetes
Kivima¨ki M, Batty GD, Hublin C (2011). PLoS Med 8(12): e1001138. doi:10.1371/journal.pmed.1001138

36. Night-shift work is associated with poorer
glycemic control in patients with type 2 DM
Manodpitipong A, et al. J Sleep Res. (2017) 26, 764–772

37. Targeted Treatment For Mediating Pathways For Hyperglycemia
Schwartz SS, et al. Diabetes Care 2016;39:179–186

38. Summary
Shift work is associated with changes in circadian
rhythm that have implications in a persons
physiology and behavior
Shift work is associated with higher risk of
subclinical hypothyroidism and its potential
consequences, especially in women
• Early screening is warranted
Shiftwork is associated with higher risk of diabetes,
possibly mediated by obesity, and poorer control of
glucose
• Management strategies that target weight management must be
included