Serum TSH Levels in Smokers and Non-Smokers. The 5th Tromsø Study

Abstract

Background: Cigarette smoking has a number of effects on the thyroid gland including the development of Graves' disease and thyroid multinodularity. However, the effect of smoking on thyroid function is more uncertain. Patients and methods: The present cross-sectional study included 6085 subjects (1744 smokers) without thyroxine medication and 441 subjects (92 smokers) with thyroxine medication that attended the 5th Tromsø study in 2001, and 460 subjects (114 smokers) that attended follow-up studies after the 5th Tromsø study. Serum TSH was measured in the 5th Tromsø study, and serum TSH, free T4, and free T3 in the follow-up studies. Comparisons between smokers and non-smokers were performed with a general linear model with age, BMI, (and gender) as covariables. Results: Serum TSH levels were significantly lower in the smokers than in the non-smokers, both in males (1.63 ± 0.88 vs. 1.95 ± 1.04 mIU/L [p < 0.01]), and in females (1.55 ± 0.86 vs. 1.86 ± 1.01 mIU/L [p < 0.01]). Serum free T4 and free T3 levels were significantly higher in smokers than non-smokers (14.0 ± 2.2 vs. 13.4 ± 2.4 pmol/L for free T4 [p < 0.05], and 3.89 ± 0.79 vs. 3.72 ± 0.67 pmol/L for free T3 [p < 0.01], males and females analyzed together). There was no association between number of cigarettes smoked and the serum TSH level. Conclusion: Smokers have lower serum TSH and higher free T4 and free T3 levels than non-smokers, which may be of importance when evaluating subjects with subclinical hypothyroidism.

Key words

Smoking - subclinical hypothyroidism - thyrotropine - triiodothyronine - thyroxine

References

• 1 Belin R M, Astor B C, Powe N R, Ladenson P W. Smoke exposure is associated with a lower prevalence of serum thyroid autoantibodies and thyrotropin concentration elevation and a higher prevalence of mild thyrotropin concentration suppression in the third national health and nutrition examination survey (NHANES III).  J Clin Endocrinol Metab. 2004;  89 6077-6086
• 2 Christensen S B, Ericsson U B, Janzon L, Tibblin S, Melander A. Influence of cigarette smoking on goiter formation, thyroglobulin, and thyroid hormone levels in women.  J Clin Endocrinol Metab. 1984;  58 615-618
• 3 Cryer P E, Haymond M, Santiago J V, Shah S D. Norepinephrine and epinephrine release and adrenergic mediation of smoking-associated hemodynamic and metabolic events.  N Engl J Med. 1976;  295 573-577
• 4 Erdogan M F. Thiocyanate overload and thyroid disease.  Biofactors. 2003;  19 107-111
• 5 Ericsson U B, Lindgarde F. Effects of cigarette smoking on thyroid function and the prevalence of goitre, thyrotoxicosis and autoimmune thyroiditis.  J Intern Med. 1991;  229 67-71
• 6 Fisher C L, Mannino D M, Herman W H, Frumkin H. Cigarette smoking and thyroid hormone levels in males.  Int J Epidemiol. 1997;  26 972-977
• 7 Jorde R, Bønaa K H, Sundsfjord J. Population based study on serum ionised calcium, serum parathyroid hormone, and blood pressure. The Tromsø study.  Eur J Endocrinol. 1999;  141 350-357
• 8 Jusko W J. Influence of cigarette smoking on drug metabolism in man.  Drug Metab Rev. 1979;  9 221-236
• 9 Kapoor D, Jones T H. Smoking and hormones in health and endocrine disorders.  Eur J Endocrinol. 2005;  152 491-499
• 10 Karakaya A, Tuncel N, Alptuna G, Kocer Z, Erbay G. Influence of cigarette smoking on thyroid hormone levels.  Human Toxicol. 1987;  6 507-509
• 11 Knudsen N, Bülow I, Laurberg P, Perrild H, Ovesen L, Jørgensen T. High occurrence of thyroid multinodularity and low occurrence of subclinical hypothyroidism among tobacco smokers in a large population study.  J Endocrinol. 2002;  175 571-576
• 13 Müller B, Zulewski H, Huber P, Ratcliffe J G, Staub J ‐J. Impaired action of thyroid hormone associated with smoking in women with hypothyroidism.  N Engl J Med. 1995;  333 964-969
• 14 Sepkovic D W, Haley N J, Wynder E L. Thyroid activity in cigarette smokers.  Arch Intern Med. 1984;  144 501-503
• 15 Vestergaard P. Smoking and thyroid disorders - a meta-analysis.  Eur J Endocrinol. 2002;  146 153-161
• 16 Utiger R D. Effects of smoking on thyroid function.  Eur J Endocrinol. 1998;  138 368-369