Interaction between cigarette smoking and iodine intake and their impact on thyroid function

P>Objective Several population-based studies in iodine-deficient areas have shown an association between smoking and thyroid function. There are no population-based studies about the effects of smoking in iodine-sufficient areas. We examined the effect of smoking on thyroid function and the association with iodine intake in Korea, an area with sufficient iodine intake, much more than recommended by the World Health Organization (WHO). Design Of 5018 subjects in a population-based cohort, we included 3399 who had no history of thyroid disease were not taking thyroid medication and whose blood samples were available for measurement of thyroid function. Measurements Thyroid function test, questionnaire about smoking status and dietary intake. Results Of 3399 subjects, 397(11 center dot 7%) had subclinical hypothyroidism (SCH). Female sex was an independent risk factor for SCH. Multivariate analysis in female subjects showed the following were independent risk factors for SCH: older age, positive antithyroid peroxidase (anti-TPO) antibody status and iodine intake, whereas current smoking was inversely related with SCH. However, in male subjects, only age showed a weak association with SCH. When the interaction between smoking and other risk factors was analysed, smoking showed no association with anti-TPO antibody status, whereas it showed a significant negative interaction with iodine intake (odds ratio, 0 center dot 930; 95% CI, 0 center dot 869-0 center dot 996; P = 0 center dot 037). Furthermore, the risk for SCH was observed only in the never-smoker group; however, it was abolished in current- and ex-smoker groups. Conclusion Cigarette smoking was associated with a lower prevalence of SCH in a negative interaction with iodine intake.Cho NH, 2009, CLIN ENDOCRINOL, V71, P679, DOI 10.1111/j.1365-2265.2009.03586.xEffraimidis G, 2009, J CLIN ENDOCR METAB, V94, P1324, DOI 10.1210/jc.2008-1548Ittermann T, 2008, EUR J ENDOCRINOL, V159, P761, DOI 10.1530/EJE-08-0386Makepeace AE, 2008, CLIN ENDOCRINOL, V69, P648, DOI 10.1111/j.1365-2265.2008.03239.xde Benoist B, 2008, FOOD NUTR BULL, V29, P195Vejbjerg P, 2008, EUR J EPIDEMIOL, V23, P423, DOI 10.1007/s10654-008-9255-1HAMPL R, 2008, ENDOCR REGUL, V42, P53Vanderver GB, 2007, THYROID, V17, P741, DOI 10.1089/thy.2006.0332Asvold BO, 2007, ARCH INTERN MED, V167, P1428Dillingham BL, 2007, THYROID, V17, P131, DOI 10.1089/thy.2006.02.06Laurberg P, 2006, EUR J ENDOCRINOL, V155, P219, DOI 10.1530/eje.1.02210Jorde R, 2006, EXP CLIN ENDOCR DIAB, V114, P343, DOI 10.1055/s-2006-924264Teng WP, 2006, NEW ENGL J MED, V354, P2783, DOI 10.1056/NEJMoa054022Messina M, 2006, THYROID, V16, P249Lim S, 2005, DIABETES RES CLIN PR, V70, P126, DOI 10.1016/j.diabres.2005.02.020Sharma RB, 2005, J IMMUNOL, V174, P7740Andersen S, 2005, AM J CLIN NUTR, V81, P656Belin RM, 2004, J CLIN ENDOCR METAB, V89, P6077, DOI 10.1210/jc.2004-0431Shin C, 2004, J HUM HYPERTENS, V18, P717, DOI 10.1038/sj.jhh.1001732YOUNJHIN A, 2004, KOREAN J COMMUNITY N, V9, P173Strieder TGA, 2003, CLIN ENDOCRINOL, V59, P396Knudsen N, 2002, ARCH INTERN MED, V162, P439, DOI 10.1001/archinte.162.4.439Hollowell JG, 2002, J CLIN ENDOCR METAB, V87, P489, DOI 10.1210/jc.87.2.489Rasmussen LB, 2002, BRIT J NUTR, V87, P61, DOI 10.1079/BJN2001474Rasmussen LB, 2001, EUR J CLIN NUTR, V55, P287, DOI 10.1038/sj.ejcn.1601156Chang HC, 2000, TOXICOL APPL PHARM, V168, P244, DOI 10.1006/taap.2000.9019Canaris GJ, 2000, ARCH INTERN MED, V160, P526Kim JY, 1998, YONSEI MED J, V39, P355Laurberg P, 1998, J CLIN ENDOCR METAB, V83, P765Rasooly L, 1998, AUTOIMMUNITY, V27, P213Divi RL, 1996, CHEM RES TOXICOL, V9, P16PARK HY, 1995, J KOREAN SOC ENDOCRI, V10, P386PRUMMEL MF, 1993, JAMA-J AM MED ASSOC, V269, P479FUKAYAMA H, 1992, ACTA ENDOCRINOL-COP, V127, P520BERGHOUT A, 1987, CLIN ENDOCRINOL, V26, P273MAHMOUD I, 1986, EXP MOL PATHOL, V44, P259TUNBRIDGE WMG, 1977, CLIN ENDOCRINOL, V7, P481