THYROREGULATORY CHANGES ASSOCIATED WITH SMOKING IN 70‐YEAR‐OLD MEN

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Abstract
Serum free T4 [tyroxine] concentrations were previously analyzed in a representative population of 70 yr old men. The effect of previous or present tobacco smoking on free T4, T4, T3 [triiodothyronine], r[reverse]T3, TSH and thyroid hormone binding proteins [TBG] was analyzed in 181 of the 460 men, excluding those with past or present goiter, those who were obviously ill or had died between 70 and 75 yr of age and those who had any disease or medication influencing free T4 concentrations. Smokers had higher T4 and rT3 levels and lower TSH levels, but T3 levels no different from non-smokers. The difference in T4 levels, but not rT3 or TSH levels, between smokers and non-smokers could be attributed to differences in body mass and to differences in TBG levels. Thus, tobacco smoking apparently is associated with long-term alterations in thyroregulatory function.