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

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 (tT3), free triiodothyronine (fT3), total thyroxine (tT4), free thyroxine (fT4), 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 tT3 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 tT3 and fT4 hormone than female smokers 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.