The influence of cigarette smoking on serum TSH concentration

Objective: To evaluate the influence of cigarettes smoking on serum TSH concentrations. Methodology: This cross sectional study included 275 patients with no history of thyroid disorder. There were 190 smokers and 85 non-smokers. The study was conducted in Prince Ali Military Hospital in Al-Karak, Jordan from September 2014 to February 2015. Blood samples were collected for serum TSH, free T4 and free T3 measurements. All statistical analysis was performed using SPSS for windows 20.0. Results: Serum TSH concentrations were significantly lower in the smokers in comparison with non-smokers (2.26±0.89 µIU/ ml Vs 2.87±0.74 µIU/ ml (p=0.029). The mean serum free T4 and free T3 concentrations were significantly higher in smokers (1.42±0.67 Vs 1.13±0.56 ng/dl (p= 0.039) and 2.75±0.97 Vs 2.32±0.66 pg/ml (p=0.041), respectively. Conclusion: We found that smokers had lower TSH and higher free T4 and free T3 levels when compared to non-smokers. Therefore, it seems that it should be taken into consideration when evaluating and treatment of subjects with subclinical hypothyroidism