Smoking-related Alterations in Serum Levels of Thyroid Hormones and Insulin in Female and Male Students

Abstract

Context Cigarette smoking has large-scale and complex effects on the endocrine system. Various studies related to cigarette smoking have provided differing results. Therefore, more research is needed to determine the effects on the body that are created by cigarette smoking. Objectives The study was designed, to investigate the effects of cigarette smoking, primarily on thyroid hormones in serum, such as on levels of total triiodothyronine (tT(3)), free triiodothyronine (fT(3)), total thyroxine (tT(4)), free thyroxine (fT(4)), thyroid-stimulating hormone (TSH) (ie, thyrotropin), and insulin of young students aged 18-25 y. Design This study was a randomized, controlled trial. Setting The study was performed in the Department of Physiology, School of Medicine, Yuzuncu Yil University (Van, Turkey). Participants Eighty healthy students, 40 females and 40 males, were included in the study. Intervention Of the 40 female participants, 25 were smokers, and 15 were nonsmokers. Of the 40 male participants, 25 were smokers; and 15 were nonsmokers. The intervention (smoking) group, therefore, consisted of 50 participants, and the control (nonsmoking) group consisted of 30 participants. Outcome Measures Serum concentrations of thyroid hormones and insulin were determined by enzyme-linked immunesorbent assays (ELISAs), using monoclonal antibodies; and by measurement of blood glucose, using a glucometer. Results The study found that both female and male smokers had higher levels of serum tT(3) and insulin hormone than nonsmokers had. A positive correlation was found between age and insulin resistance in male smokers. The study also found that male smokers had higher levels of serum tT(3) and fT(4) hormone than female smoken had. Conclusions Smoking may be associated with an increased Secretion of thyroid hormones and the development of insulin resistance. With aging, insulin resistance may increase more in male smokers than in female smokers.