Thyroid hormone levels and cigarette smoking in baboons.
Using a primate animal model, two studies were undertaken to examine the effects of cigarette smoking on thyroid hormone levels. In study 1, mean total triiodothyronine (total T3) and mean total thyroxine (total T4) levels were measured in two groups of baboons (Papio cynocephalus) who were taught to smoke cigarettes using operant conditioning techniques. The smokers were divided into established and naive smokers according to pack-years of exposure. A control group of never-smoker baboons was included for comparison. Blood sampling was done after long-term cigarette consumption and again 1 week after cigarette deprivation. In the naive smoker group, mean total T3 concentrations were reduced below control group values (P less than 0.05). After cigarette deprivation for 1 week, mean total T3 values returned to normal. No significant differences in total T4 levels were observed in either group. In study 2, we assessed some other indices of thyroid function. The same groups of baboons were divided into good and poor smokers by plasma cotinine and blood carboxyhemoglobin (% COHb) levels during 28 weeks of cigarette smoking activity. Immediate fluctuations and reductions in total T3 levels were observed that were not accompanied by reductions in total T4. The animals were then cigarette deprived for 1 week and blood samples were obtained every other day during this period. Significant increases in total T3 concentrations were observed in poor smokers immediately after cessation. Both groups also exhibited significant reductions (P less than 0.05) in T3 uptake and free T4 index (FT4I) when compared to control group values. These data suggest that poor smokers are more susceptible to thyroid hormone level shifts than more established smokers, since the established smokers become habituated to the compounds contained in cigarette smoke through repeated exposure.
Sepkovic
D W
DW
American Health Foundation, Naylor Dana Institute, Valhalla, New York 10595.
Marshall
M V
MV
Rogers
W R
WR
Cronin
P A
PA
Colosimo
S G
SG
Haley
N J
NJ
D000818:Animals; D002263:Carboxyhemoglobin / Q000378:metabolism; D003367:Cotinine / Q000097:blood; D010215:Papio / Q000097:blood*; D012907:Smoking; D013974:Thyroxine / Q000097:blood*; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood*
D014284:Triiodothyronine; D002263:Carboxyhemoglobin; D003367:Cotinine; D013974:Thyroxine