Thyroid Function and Cancer Risk: A Prospective Population Study
- Alf Inge Hellevik1,
- Bjørn Olav Åsvold1,3,
- Trine Bjøro4,
- Pål R. Romundstad1,
- Tom Ivar L. Nilsen2 and
- Lars J. Vatten1,5
- 1Department of Public Health, Faculty of Medicine and 2Human Movement Science Programme, Norwegian University of Science and Technology, 3Department of Medicine, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway; 4Department of Medical Biochemistry, Rikshospitalet University Hospital and University of Oslo, Oslo, Norway; and 5International Agency for Research on Cancer, Lyon, France
- Requests for reprints:
Bjørn Olav Åsvold, Department of Public Health, Faculty of Medicine, Norwegian University of Science and Technology, N-7489 Trondheim, Norway. Phone: 47-9246-6240; Fax: 47-7359-7577. E-mail: bjorn.o.asvold{at}ntnu.no
Abstract
Background: It has been hypothesized that thyroid function may influence cancer risk, but few studies with adequate statistical power have investigated this question, and the results have not been consistent.
Methods: In a prospective study of 29,691 people (19,710 women and 9,981 men) without previously known thyroid disease, thyrotropin was measured at baseline, and cancer incidence was recorded during 9 years of follow-up. Using Cox regression analysis, we studied the associations (hazard ratios) of thyrotropin categories with total cancer risk, and specifically, with risk of lung, colon, prostate, and breast cancer adjusted for age, sex, and smoking status.
Results: Low thyrotropin levels (<0.50 mU/L) were associated with increased cancer risk [adjusted hazard ratio (HR), 1.34; 95% confidence interval (CI), 1.06-1.69] compared with the euthyroid reference group. The higher risk was driven by lung cancer (adjusted HR, 2.34; 95% CI, 1.24-4.40) and prostate cancer (adjusted HR, 1.97; 95% CI, 1.04-3.76). After excluding the first 2 years of follow-up, the associations were strengthened to 2.91 (1.49-5.70) for lung cancer and 2.60 (1.36-4.99) for prostate cancer.
Conclusion: Thyrotropin levels suggestive of hyperthyroid function are associated with increased cancer risk, and specifically, with increased risk of lung and prostate cancer, whereas hypothyroid function does not seem to be associated with cancer risk. (Cancer Epidemiol Biomarkers Prev 2009;18(2):570–4)
Footnotes
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Grant support: Norwegian Research Council; Norwegian University of Science and Technology; and the Central Norway Regional Health Authority. The funders had no role in the conduction of this study.
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- Accepted December 1, 2008.
- Received September 28, 2008.
- Revision received November 22, 2008.
