Brief report: A brief exposure to moderate passive smoke increases metabolism and thyroid hormone secretion

Abstract

Context: Active smoking influences normal metabolic status and thyroid function. Objective: The objective was to assess experimentally the effects of 1 h of moderate passive smoking in a controlled simulated bar/restaurant environment on the metabolism and thyroid hormone levels in healthy nonsmokers. Participants: Eighteen (nine females, nine males) healthy individuals (mean ± SD: age, 25.3 ± 3.1 yr; height, 174.0 ± 10.1 cm; weight, 65.2 ± 13.7 kg) participated in the study. Design: In repeated-measures randomized blocks, participants visited the laboratory on 2 consecutive days. In the experimental condition, they were exposed to 1 h of moderate passive smoking at a carbon monoxide concentration of 23 ± 1 ppm in an environmental chamber, whereas in the control condition participants remained in the same chamber for 1 h breathing normal atmospheric air. Main Outcome Measures: In both conditions, cotinine serum and urine levels, resting energy expenditure (REE), as well as concentration of T3, free T 4, and TSH were assessed before participants entered the chamber and immediately after their exit. Heart rate and blood pressure were tested in 10-min intervals during all REE assessments. Results: The mean ± SD difference of serum and urine cotinine levels (-0.27 ± 3.94 vs. 14.01 ± 6.54 and 0.05 ± 2.07 vs. 7.23 ± 3.75, respectively), REE (6.73 ± 98.06 vs. 80.58 ± 120.91) as well as T3 and free T4 (0.05 ± 0.11 vs. 0.13 ± 0.12 and 0.02 ± 0.15 vs. 0.22 ± 0.20) were increased in the experimental compared with the control condition at baseline and follow-up (P < 0.05). No statistically significant variation was observed in the mean difference of the remaining parameters (P > 0.05). Serum and urine cotinine values were linearly associated with REE (P < 0.05). Conclusion: One hour of passive smoking at bar/restaurant levels is accompanied by significant increases in metabolism and thyroid hormone levels. Copyright © 2007 by The Endocrine Society.