Cigarette smoking and the thyroid

Abstract

The effects of smoking on the function of endocrine glands have been investigated extensively but still are to be elucidated fully. It is widely recognized that the most important component of the smoke produced from the burning of tobacco, in terms of endocrine effects, is nicotine. Nicotine acts through the interaction with acetylcholine receptors, but it seems likely that others among the numerous smoke products may somehow influence endocrine homeostasis.The present paper will focus on the relationship between smoking and variations in thyroid economy or the occurrence of thyroid dysfunction. Thyroid functionSeveral studies have been carried out to ascertain whether smoking is associated with variations in thyroid economy. The rationale for these investigations was dictated by the observation that smoking is associated with a decrease in body mass, and, conversely, refrain from smoking is often accompanied by an increase in body mass (1). These changes might be mediated by variations in appetite and food intake but might also be linked to smoking-induced alterations in thyroid function. Melander et al. reported that cessation of smoking was associated with a small decrease in serum T4, reverse T3 (rT3) and a small increase in serum TSH levels, while serum T3 concentration was not altered significantly (2). These data were interpreted as being suggestive of the fact that cigarette smoking might stimulate thyroid function, which would be readjusted following smoking with¬ drawal. The fact that serum T3 levels were unchanged was interpreted as indicative of a selective stimulation of T4 secretion or, alternatively, of an increased T3 clearance caused by smoking.Results obtained in subsequent studies are far from unequivocal, because T3 has been reported to be increased (3-5), unchanged (6-8) or slightly decreased (9, 10). Likewise, serum T4 has been found to be increased (6), normal (3-5, 7) or decreased (9, 10). Serum TSH concentrations in most cases were unchanged (3-5, 8) but also decreased values have been found (6, 7, 10). Interestingly, Sepkovic et al. observed that changes in T3, T4 and TSH concentra¬ tions were more pronounced in heavy smokers than in light-to-moderate smokers, while plasma thiocyanate levels progressively increased with the degree of smoking, implying a relationship between the increased absorption of cigarette smoke thiocyanate and the changes occurring in thyroid economy (9). The conflicting results in the different series are not readily explainable. Several factors may have affected the results, including enrolment of heavy vs moderate smokers, the evaluation of short-term vs long-term effects and differences in age and body mass. In addition, differences might be related to the relative contribution of opposite mechanisms. If sympathetic nervous stimulation is prevailing, this might lead to stimulation of thyroid hormone secretion (11) and, in turn, to a decreased TSH release. On the other hand, the presence of substances in cigarette smoke that stimulate drug metabolism (12) might...

Effect of passive smoking on thyroid function in infants

“…This was associated with an increase in serum TG and thiocyanate concentrations (7). The increase in the thyroid volume/birth weight ratio observed in newborns appeared to parallel the increase in cord serum thiocyanate concentrations found in infants of smoking mothers, suggesting that…”

“…Effect of passive smoking on thyroid function 381 smoking during pregnancy may be a relevant cause of thyroid gland enlargement in the newborn (5), probably by reducing iodine availability (7). As no significant influence of parental smoking on the development and growth of the children was observed, study of the effects of passive smoking on thyroid function should be extended to older children, in order to evaluate whether a relation exists between altered thyroid function and behavioural problems observed in children exposed to passive smoking (21,22).…”

“…Thiocyanate, derived from hydrogen cyanide, leads to increased excretion of iodine, seems to inhibit iodine uptake by the thyroid, and can have a goitrogenic effect in the presence of iodine deficiency (5)(6)(7).…”

Thyroid Disruptors: How They Act and How We React

“…These include minor and probably physiologically unimportant alterations in thyroid hormones (Christensen et al 1984;Hegedus et al 1985;Karakaya et al 1987;Lio et al 1989;Petersen et al 1991;Hegedus et al 1992;Melander et al 1981;Eden et al 1984;Sepkovic, Haley, and Wynder 1984;Nystrom et al 1993) and thyrotropin concentrations (Christensen et al 1984;Hegedus et al 1985;Karakaya et al 1987;Lio et al 1989;Petersen et al 1991;Hegedus et al 1992;Melander et al 1981;Eden et al 1984;Sepkovic, Haley, and Wynder 1984), central (thyroid) and peripheral antithyroid actions (Muller et al 1995;Utiger 1995), thyroid gland stimulation or goitrogenic effects (Christensen et al 1984;Hegedus et al 1985;Lio et al 1989;Ericsson and Lindgarde 1991), carcinogenic properties (McTiernan, Weiss, and Daling 1984;Ron et al 1987;Kolonel et al 1990;Preston-Martin et al 1993;Shore et al 1993;Hallquist et al 1994;Galanti et al 1996;Rossing et al 2000;Hallquist et al 1993;Kreiger and Parkes 2000) and also an increase in the susceptibility to Graves´ disease (Bartalena et al 1995;Bufalo et al 2008;…”

Novel Approaches to the Management of Graves` Ophthalmopathy

“…At present, preventive intervention can only be carried out on exogenous risk factors. The latter include cigarette smoking 96 , thyroid dysfunction, both hyper- 97,98 and hypothyroidism 99 and radioiodine therapy for hyperthyroidism [100][101][102] .…”