Influence of smoking on thyroid activity

Cigarette smoking is associated with higher thyroid hormone and lower TSH levels: the PREVEND study

PURPOSE

The extent to which smoking is associated with thyroid stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) when taking account of clinical variables including alcohol consumption is unclear. We aimed to determine associations of TSH, FT4, and FT3 levels with current smoking.

METHODS

A cross-sectional study was performed in 5766 euthyroid participants (Prevention of Renal and Vascular End-Stage Disease cohort). Current smoking was determined by self-report, categorized as never, former, and current (≤20 and >20 cigarettes per day). Smoke exposure was determined by urinary cotinine.

RESULTS

Current smoking of ≤20 and >20 cigarettes per day was associated with lower TSH and higher FT3 levels. FT4 levels were higher in subjects smoking <20 cigarettes per day vs. never and former smokers. Current smokers also consumed more alcohol. Multivariable linear regression analyses adjusted for age, sex, anti-TPO autoantibody positivity, alcohol consumption, and other variables demonstrated that lower TSH, higher FT4 and higher FT3 were associated with smoking ≤20 cigarettes per day vs. subjects who never smoked (P < 0.001, P = 0.018, and P < 0.001, respectively) without a further significant incremental effect of smoking >20 cigarettes per day. In agreement, TSH was inversely, whereas FT4 and FT3 levels were positively associated with urinary cotinine (P < 0.001 for each). In contrast, alcohol consumption >30 g per day conferred higher TSH and lower FT3 levels.

CONCLUSIONS

Cigarette smoking is associated with modestly higher FT4 and FT3, and lower TSH levels, partly opposing effects of alcohol consumption.

Impact of smoking on thyroid gland: dose-related effect of urinary cotinine levels on thyroid function and thyroid autoimmunity

Cigarette smoking is believed to affect thyroid function and autoimmune thyroid disease. However, there is little information to analyze their association using objective biomarkers. The aim of this study was to investigate the dose-related effect of smoking on thyroid hormones and thyroid peroxidase antibody (TPO Ab) using urinary cotinine levels and a population-based cohort. The present study used the thyroid hormone and urinary cotinine dataset from sixth Korean National Health and Nutrition Examination Survey in 2014 and 2015, and a total of 4249 participants were included. Dose-response relationships between thyroid hormone (free T4, TSH, and TPO Ab) and urinary cotinine levels were estimated using ANCOVA after adjustment for all variables (age, height, weight, alcohol, exercise, and log- transformed iodine in urine). Urinary cotinine level was negatively correlated with TSH. The estimated coefficients were −0.0711 in males and −0.0941 in females (p < 0.0001). TPO Ab titer was positively correlated with cotinine levels in males (p < 0.0001). Our findings indicated a significant dose-related effect of urinary cotinine level on thyroid function, and thyroid autoimmunity.

Cigarette Smoke Extract Disrupts Transcriptional Activities Mediated by Thyroid Hormones and Its Receptors

Cigarette smoke contains over 4800 compounds, including at least 200 toxicants or endocrine disruptors. Currently, effects of cigarette smoke on thyroid hormone (TH) levels remains to be clarified. Here, we demonstrate that cigarette smoke extract (CSE) possesses thyroid hormone properties and acts synergistically as a partial agonist for thyroid hormone receptors (TRs) in the presence of TH. In transient gene expression experiments, CSE stimulated transcriptional activity with TH in a dose-dependent manner. Stimulatory effects were observed with physiological TH concentrations, although CSE did not activate TRs without TH. CSE (5%) dissolved in phosphate-buffered saline (PBS) supplemented with 1 nM TH was approximately comparable to 3.2±0.1 and 2.3±0.2 nM of TRα1 and TRβ1, respectively. To illustrate probable mechanisms of the CSE agonistic activity, effects on TR mediated transcriptional functions with cofactors were investigated. With a mammalian two-hybrid assay, CSE recruited the nuclear coactivators glucocorticoid receptor interacting protein 1 (GRIP1) and steroid receptor coactivator 1 (SRC1) to the TR. Unsaturated carbonyl compounds, acrolein, crotonaldehyde, and methyl vinyl ketone, representative constituents of CSE, retained such agonistic properties and possibly contributed to stimulatory effects. The results suggest that CSE recruits a transcriptional activator and may reinforce TH binding to the TR additively, resulting in gene expression. CSE partially agonizes TH action and may disturb the function of various nuclear hormone receptor types and their cofactors to disrupt the physiological processes.

Relationship of Gender and Smoking History in the Development of Hypothyroidism From Exposure to External Beam Radiation for Head and Neck Cancers

Background

Patients with head and neck cancers (HNCs) are often treated with external beam radiation therapy (XRT). Unfortunately this therapy is not without its unintended consequences. One of these side effects includes the development of radiation-induced hypothyroidism. Our study is designed to pay special attention to variables like gender and smoking history and analyze their relationship with the development of hypothyroidism.

Methods

Patients’ charts were reviewed over a period of 13 years from January 1, 2000 to November 30, 2013 to gather information on patients who had previously received XRTs for HNCs. We used the Tumor Registry Database at the University of Florida, College of Medicine in Jacksonville for this retrospective review. Patient characteristics were examined including age, gender, race/ethnicity and smoking history. Special attention was paid to the development of hypothyroidism (thyroid stimulating hormones > 5.0 with appropriate decrease in free serum T4) levels after exposure to XRT for HNCs. Results were then analyzed using the univariate statistical analysis which was done using the SAS software using a 0.05 alpha level of significance expressed in terms of odds ratio (OR) with 95% confidence intervals (CIs).

Results

We found a total of 1,116 patients in our database who have received XRTs for HNCs. Out of these 72 (6.45%) patients developed hypothyroidism. Out of 263 African American patients 20 (7.6%) had hypothyroidism, whereas 49 (6%) out of 819 white people had this outcome. As for gender 32 out of 341 females (9.4%) and 40 out of 775 males had hypothyroidism. Thirty-five out of 544 (6.4%) with no family history and 19 (2.4%) out of 205 (9.3%) with positive family history for cancer had the outcome too. Finally 43 (6.5%) out of 664 smokers and 17 (8.3%) out of 206 non-smokers were found to develop hypothyroid as well. Both groups were found to have homogenous average age at diagnosis. When the univariate analysis was conducted, the strongest predicting variable was gender as hypothyroid patients were 1.90 (95% CI 1.17 - 3.09) times more likely to be females, and these results were statistically significant with P value of 0.008. More patients tended to be African Americans with OR 1.21 (CI 0.822 - 1.78), had positive family history of cancer (negative family history had OR 0.67 (CI 0.38 - 1.21), and less likely to be smokers (OR 0.77 (0.43 - 1.38). However, race, family history of cancer and smoking history did not achieve any statistical significance as evident by the P values.

Conclusion

In our patient population, females were more likely to develop radiation-induced hypothyroidism.

Effect of maternal nicotine/thiocyanate exposure during gestational period upon pituitary, thyroid and parathyroid function/morphology of 1-month-old rat offspring

INTRODUCTION

Impact of in utero exposure to nicotine, on the structure of the thyroid-pituitary axis and the parathyroid glands have been examined in 1-month-old rats and compared with that of thiocyanate.

MATERIALS AND METHODS

Three pregnant female groups were used; control, nicotine and thiocyanate. Treatment started from gestation day (4-20) and the specimens were harvested from the male offspring of all groups at the age of 1 month and processed for light, electronmicroscopic and immunohistochemical examination. Total triiodothyronine (tT3), total thyroxine (tT4) and total thyrotropin (TSH) were quantitatively determined in serum.

RESULTS

Both nicotine and thiocyanate activated the thyroid follicular cells, with an increase in height (about 30 %) and a negative feedback on the pituitary thyrotrophs which revealed a reduction in the number of cytoplasmic secretory granules, particularly the thiocyanate group. However, in thiocyanate group there was signs of impaired secretory activity of the thyroid gland. The arbitrary area of parathyroid chief cells, increased (about 45 %) particularly in nicotine group, with signs of reduced activity and a positive feedback on the parafollicular cells which revealed hypertrophy, proliferation (25 %) and increased intensity of positive immunohistochemical reaction for calcitonin.

CONCLUSION

Nicotine impaired chief parathyroid cells activity and consequently activated parafollicular cells. Thiocyanate reduced pituitary thyrotrophs activity, whereas both nicotine and thiocyanate increased thyroid follicular cells activity. This impact of in utero exposure persisted for 1-month postnatal.

Monoamine oxidase activity and tri-iodothyronine level in violent offenders with early behavioural problems

The focus is on evaluating the relationships between early behavioural problems and biochemical variables at adult age and their significance for early criminality and violent behaviour in a life perspective. In the present study, using prospective longitudinal data, a sample of males with a history of early criminal behaviour and male controls (n = 103) were investigated concerning (1) teacher-rated behaviours at age 11-14 years; (2) platelet monoamine oxidase (MAO) activity and tri-iodothyronine (T(3)) level at adult age; (3) registered early criminality (11-14 years); (4) records of violent offending up to age 35 years, and (5) interview data on smoking. The main finding was that a combined risk level pattern of low MAO activity and high T(3) level was found significantly more frequently than expected in violent offenders with an early behavioural risk pattern. Furthermore, there was a significant interaction effect between early attention difficulties and smoking on MAO activity, as well as an effect by smoking on MAO activity. The findings are discussed in terms of the possible influence of biological vulnerability to certain behaviours, which in combination with possible childhood stress, enhance the risk for antisocial behaviours and subsequent violence.

Breast cancer incidence in ex-smokers in relation to body mass index, weight gain and blood lipid levels

According to several studies breast cancer is more common among former smokers. This study explores whether this association has any relationship with anthropometric measurements or blood lipid levels. The 2082 ex-smokers (mean age 49.9 years) in the Malmö Preventive Cohort were followed for an average of 13.3 years using official cancer registries. This yielded 93 incident breast cancer cases. Oestrogen receptor (ER) status was assessed by an immunological method. Incidence of breast cancer covaried with height, body mass index, weight gain and cholesterol levels. None of these associations reached statistical significance. Incidence of breast cancer increased over quartiles of serum triglycerides, Ptrend: 0.02, relative risk (RR) for triglycerides as a continuous variable: 1.46 (1.21-1.77). Nineteen tumours were ER negative; this subgroup was similarly related to high triglycerides, 1.76 (1.40-2.21). All results were similar when BMI and cholesterol levels were entered into the model. It is concluded that breast cancer incidence covaries with triglyceride levels in ex-smokers.

Prevalence and relevance of thyroid dysfunction in 1922 cholesterol screening participants

Controversy persists about the role of subclinical hypothyroidism in hypercholesterolemia. This study aimed to assess in a clinically healthy, middle-aged population of employees the prevalence of thyroid function disorders and their relation to demographic variables and cardiovascular risk factors. 1922 (former) employees were screened with follow-up of newly identified cases of undiagnosed (subclinical) hypothyroidism and hyperthyroidism. Thyroid stimulating hormone (TSH), prevalence and course of (subclinical) hypo- and hyperthyroidism and their relation to cardiovascular risk factors (cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, smoking, systolic and diastolic blood pressure) were assessed. The prevalence of newly diagnosed subclinical hypothyroidism (cut-off TSH concentration: 4.0 mU/L) was 1.1% (17 women and 5 men) with a mean TSH concentration of 7.37 (95% CI 5.18-9.56) mU/L. No case of overt hypothyroidism could be diagnosed. Elevated levels of antibodies to microsomal or thyroglobulin antigens were detected in six subjects with subclinical hypothyroidism (27.3%). Fifteen subjects (0.8%, 13 women and 2 men) had TSH concentrations below 0.1 mU/L. The cardiovascular risk profile of subjects with mild subclinical hypothyroidism was not different from subjects with normal TSH levels. The prevalence of subclinical hypothyroidism was 0.8% in normocholesterolemic (cholesterol <5.2 mmol/l) and 1.4% in hypercholesterolemic subjects (n.s.). One woman each with the subclinical form of the disease developed hypothyroidism or hyperthyroidism after 21 and 11 months of follow-up, respectively. Subclinical hypothyroidism and subclinical hyperthyroidism were rarely observed in a target group for coronary heart disease prevention. Mild subclinical hypothyroidism was not associated with any adverse cardiovascular risk profile. These results argue against indiscriminate measurements of TSH concentrations in clinically healthy subjects either with normocholesterolemia or hypercholesterolemia.

The effect of nicotine on thyroid function in rats

Very recently, it has been reported that subclinical hypothyroidism is more severe and peripheral markers of hypothyroidism are more pronounced in women with subclinical or overt hypothyroidism who smoke. Increased concentrations of the known goitrogen thiocyanate, generated from cigarette smoke, have been the major explanation for the decreased thyroid function in these women but do not explain the reported increased peripheral markers of hypothyroidism. There are no data on the effect of the other major product of cigarettes, nicotine, on thyroid function in vivo. The present studies were therefore performed to determine the effects of large doses of nicotine infused for 7 days on thyroid function, outer-ring 5'deiodinase activity (5'D-I), and hepatic malic enzyme activity (a measure of thyroid hormone action) in euthyroid, subclinically hypothyroid (hemithyroidectomized), and L-thyroxine (L-T4)-treated thyroidectomized rats. Nicotine infusion had no effect on serum T4, triiodothyronine (T3), thyrotropin (TSH), and cholesterol concentrations, intrathyroidal metabolism of 125I, liver and kidney 5'D-I activity, and hepatic malic enzyme activity in euthyroid and subclinically hypothyroid rats. Nicotine administration also did not affect serum T3, TSH, or cholesterol concentrations, liver and kidney 5'D-I activity, and hepatic malic enzyme activity in L-T4-treated thyroidectomized rats. These studies provide strong evidence that nicotine is not responsible for the observed adverse effects of smoking on the thyroid in humans.

Relationship between cigarette smoking and hypothyroidism in patients with Hashimoto's thyroiditis

This retrospective study examined the relationship between smoking history and thyroid function in 387 women patients with Hashimoto's thyroiditis (mean age +/- SD = 50.5 +/- 12.7 yr). The same analysis was done in 238 randomly chosen women patients with nodular goiters (mean age = 45.3 +/- 14 yr) and 166 control women (mean age = 47.7 +/- 14.2 yr). In patients with Hashimoto's thyroiditis, there were 256 non smokers, 110 smokers, and 21 smokers. Among the 110 smoking patients with Hashimoto's thyroiditis, 76.4% were hypothyroid, whereas the prevalence of hypothyroidism was 34.8% among the 256 non smokers. Among the 21 ex-smokers with Hashimoto's thyroiditis, the majority of patients (61.9%) were hypothyroid, suggesting that cessation of smoking does not appear to reverse hypothyroidism. The percentages of smokers in the hypothyroid group, the subclinical hypothyroid group, and the euthyroid group were 45.2%, 18%, and 11.3%, respectively, in patients with Hashimoto's thyroiditis. The greatest serum levels of thiocyanate (an antithyroid substance generated by smoking) were found in those who both smoked and had hypothyroidism. Thus, an increase in serum thiocyanate concentration from smoking may contribute to the development of hypothyroidism in patients with Hashimoto's thyroiditis. Smoking related hypothyroidism was not seen in patients with nodular goiters. Our results suggest that smoking may increase the risk of hypothyroidism in patients with Hashimoto's thyroiditis.

Criminality and psychopathy as related to thyroid activity in former juvenile delinquents

Levels of triiodothyronine (T3) and thyroid-stimulating hormone (TSH), psychopathy-related personality traits and criminality from the age of 15 years onward were examined in 70 former juvenile delinquents and 35 control subjects aged 38-46 years. T3 levels were significantly associated with criminality but not with psychopathy-related personality traits. TSH levels were not related to any of these variables. Juvenile delinquents who displayed persistent criminal behaviour were found to have higher mean T3 levels than juvenile delinquents who did not display criminality in adulthood and non-criminal controls. Former juvenile delinquents with T3 levels above the mean level found in the controls were registered for criminality 3.8 times more often than juvenile delinquents with T3 levels below the mean level found in the control group. The results are discussed in terms of elevated T3 levels representing a compensatory or stress phenomenon for low social adaptive ability of individuals who display persistent criminal behaviour.

Impaired action of thyroid hormone associated with smoking in women with hypothyroidism

BACKGROUND

The effect of smoking on thyroid function is controversial, and its effect on thyroid hormone action is unknown. We investigated the effects of cigarette smoking in women with various grades of hypothyroidism and in normal women.

METHODS

We studied 138 normal women and 135 women with primary hypothyroidism, of whom 84 had subclinical hypothyroidism and 51 overt hypothyroidism. Sixty of the women with hypothyroidism were reevaluated during thyroxine therapy. The women were categorized as smokers or nonsmokers according to their responses to a questionnaire. Thyroid function was evaluated by measurements of serum thyrotropin, free thyroxine, and triiodothyronine. Peripheral thyroid hormone action was assessed by a clinical score and measurements of ankle-reflex time and serum lipids and creatine kinase.

RESULTS

Among the women with subclinical hypothyroidism, the smokers had a higher mean (+/- SD) serum thyrotropin concentration (21.3 +/- 16.6 vs. 12.7 +/- 7.2 mU per liter, P = 0.004) and a higher ratio of serum triiodothyronine to serum free thyroxine (by 30 percent, P = 0.003) than the nonsmokers. Their serum concentrations of total cholesterol and low-density lipoprotein (LDL) cholesterol were higher (by 16 percent, P = 0.013; and 28 percent, P = 0.003, respectively). Among the women with overt hypothyroidism, the serum concentrations of thyrotropin, free thyroxine, and triiodothyronine were similar in the smokers and nonsmokers. As compared with the nonsmokers, the smokers had a clinical score indicating a greater degree of hypothyroidism (P < 0.001), higher serum concentrations of total and LDL cholesterol (by 25 percent, P < 0.001; and 24 percent, P = 0.002, respectively), longer ankle-reflex time (by 25 percent, P < 0.001), and higher serum concentrations of creatine kinase (by 236 percent, P < 0.001). There were dose-response relations between smoking and serum concentrations of total and LDL cholesterol, serum creatine kinase concentrations, and ankle-reflex time in the women with overt hypothyroidism, and between smoking and serum concentrations of total and LDL cholesterol in the women with subclinical hypothyroidism.

CONCLUSIONS

Smoking increases the metabolic effects of hypothyroidism in a dose-dependent way. This may be explained by alteration of both thyroid function and hormone action.

A case-control study of maternal risk factors for thyroid cancer in young women (California, United States)

A population-based case-control interview study investigated whether reproductive factors are related to the striking female-over-male excess of thyroid cancer among women of reproductive age in Los Angeles County, CA (United States). As a separate component of that study, mothers of 153 cases and 140 controls who were age 40 or younger at diagnosis or reference date were interviewed by telephone to determine the significance of family and maternal risk factors in the subsequent development of thyroid cancer among the daughters. More case than control mothers experienced miscarriage prior to the index pregnancy (odds ratio [OR] = 2.0, 95 percent confidence interval [CI] = 1.1-3.5). Increased risk was associated with family history of thyroid cancer or other thyroid disease (OR = 2.1, CI = 1.2-3.6). More control than case mothers smoked during the index pregnancy (OR = 0.6, CI = 0.4-1.0); however, among mothers who smoked, case mothers smoked more. Case mothers experienced a greater increase in weight from minimum adult weight to weight at index pregnancy (P for trend = 0.01). Reports from mothers also confirmed the risk associated with the daughter's exposure to ionizing radiation from birth through adolescence; ionizing radiation remains the best-established risk factor for thyroid cancer.

Cigarette smoking and the thyroid

Relevant English language articles published from 1970 through 1993 regarding the possible influence of cigarette smoking on the thyroid were identified through a MEDLINE search and manual searches of identified articles. Thiocyanate in tobacco smoke influences the thyroid by a competitive inhibition of iodine uptake and organification in the gland. Also the stimulation of the sympathetic nervous system by cigarette smoke and benzpyrene, another constituent of tobacco, is thought to influence thyroid gland function. The thyroid hormones and TSH receptor autoantibodies are not affected by smoking, but serum TSH levels have been found to be slightly reduced. Smokers have a higher frequency of goiter and increased serum thyroglobulin levels, especially in iodine-deficient areas. Graves' ophthalmopathy is strongly associated with cigarette smoking; the more severe the eye disease the stronger the association. Graves' disease without ophthalmopathy is also associated with smoking, though this association is weaker. Thiocyanate level in cord blood equilibrates completely with the level in the mother, and a reverse correlation has been demonstrated between birth weight and thiocyanate level in cord blood. Cigarette smoking induces similar changes in thyroid function in the adult and the fetus. No separate study has elucidated the effects of cessation of smoking, but there seems to be longstanding effects induced by smoking, some probably irreversible.

Smoking cessation and change in diastolic blood pressure, body weight, and plasma lipids. MRFIT Research Group

Cigarette smoking cessation was examined for its impact on diastolic blood pressure, weight, and plasma lipids in 3,470 special intervention males in the Multiple Risk Factor Intervention Trial. Change in smoking status (quitters vs nonquitters) was not independently associated with change in diastolic blood pressure or the subsequent use of antihypertensive medication for smokers who were normotensive at entry. More quitters (35%) became hypertensive than nonquitters (27%, P less than 0.01), although the groups had similar baseline diastolic blood pressure levels. Weight gain subsequent to cessation probably contributed to this excess incidence of hypertension in quitters. Stepped-care antihypertensive therapy lowered diastolic blood pressure similarly for hypertensive quitters and nonquitters. Weight increases of 6 lb or more by the 72-month visit occurred in 47% of quitters vs 25% of nonquitters (P less than 0.01); quitters did not differ from nonquitters in their change in total kilocalories from baseline to the 72-month visit. Quitters who gained 6 lb or more tended to be less obese at baseline, be less physically active, and smoke more cigarettes per day than those who did not gain this amount. Finally, quitters relative to nonquitters experienced an adjusted increase of 2.4 mg/dl high-density lipoprotein cholesterol, but no difference in total or low-density lipoprotein cholesterol. The implications for intervention are discussed as they relate to the common, but not inevitable, increase in weight subsequent to cessation.

Thyroid disease in middle-aged and elderly Swedish women: thyroid-related hormones, thyroid dysfunction and goitre in relation to age and smoking

The prevalence of thyroid disease and the concentration of thyroid hormones and thyrotropin were studied in a random population sample of 1154 women, aged 50-72 years, with special reference to the effect of age and smoking. The prevalence of spontaneous hypothyroidism was 3.3% (previously unknown overt and mild disease 1.3%) and the prevalence of hyperthyroidism was 2.5% (previously unknown disease 0.2%). Clinically suspected hyper- or hypothyroidism (very weak to strong) was recorded in 288 women, but was only verified in three cases. The prevalence of visible and palpable thyroid enlargement was 2.1% and 13-14%, respectively. Total thyroxine concentrations increased and free tri-iodothyronine levels decreased significantly with age (P less than 0.001). The serum thyrotropin concentrations were lower in smoking women than in non-smokers in the 50- and 58-year age groups (P less than 0.05). There was no increase in the prevalence of thyroid disease or goitre in the women who were smokers at the time of the study.

Relationships between weight and caloric intake of men who stop smoking: the Multiple Risk Factor Intervention Trial

Data from 6,569 middle-aged men in the Multiple Risk Factor Intervention Trial were analyzed to determine whether the weight change associated with smoking cessation resulted primarily from appetite or metabolic alterations. The appetite hypothesis attributes weight gain to an enhanced appetite and subsequent increase in caloric intake. The metabolic change hypothesis attributes weight gain to a metabolic alteration and subsequent decrease in basic caloric needs. Caloric intake and weight changes were tabulated for men who quit smoking and were compared to similar changes in men who continued smoking over 12 months. The difference between caloric intake changes in men quitting smoking versus men continuing smoking, controlled for weight change, was attributed to the metabolic change hypothesis. Men who quit smoking consumed 103 calories per day less (95% confidence interval = 29 to 177) than men who continued smoking with similar body weight changes. The decrease in caloric intake attributed to smoking cessation was proportional to the number of cigarettes smoked prior to cessation [corrected].

Effects of cigarette smoking on thyroid function and the prevalence of goitre, thyrotoxicosis and autoimmune thyroiditis

The effect of smoking habits on thyroid function and the prevalence of thyroid diseases was studied in two birth cohorts (1928 and 1941) of men and women. A total of 1555 individuals (836 men and 719 women) were smokers. 1048 individuals (604 men and 444 women) were ex-smokers and 1497 individuals (560 men and 937 women) were non-smokers. The serum thyrotropin (TSH) concentration was significantly lower in smokers than in ex-smokers and non-smokers (P = 0.05 and P = 0.001, respectively). Smoking habits did not affect the serum triiodothyronine (T3) concentrations. The prevalence of non-toxic goitre and toxic diffuse goitre was significantly higher in smoking women than in non-smoking women (P = 0.005 and P = 0.04, respectively). Thiocyanate may be the goitrogenic factor responsible for the increased prevalence of non-toxic goitre. The cause of the increased prevalence of toxic diffuse goitre is less obvious. Hypothetically, an increase in sympathetic activity in smokers may promote the development of thyrotoxicosis in predisposed individuals, but immunological disturbances caused by smoking are another possibility.

More on smoking habits and Graves' ophthalmopathy

Since a relationship between cigarette smoking and the occurrence of Graves' ophthalmopathy has been recently postulated, we reviewed the smoking habits of 1730 women, including subjects without thyroid disease, with nontoxic goiter (NTG), toxic nodular goiter or toxic adenoma (TNG), Hashimoto's thyroiditis (HT), Graves' disease without ophthalmopathy (GD) or with ophthalmopathy (GO). The prevalence of smokers in NTG, TNG and HT was about 30%, not different from that of controls. Smokers were 47.9% in GD and 64.2% in GO groups. The latter figures were highly different from those of the other groups and also from each other. The percentage of heavy smokers was higher in patients with more severe ophthalmopathy. No clear explanation for this phenomenon can be offered. The absence of a high prevalence of smokers among patients with non-toxic goiter, nonautoimmune hyperthyroidism and Hashimoto's thyroiditis, limits the impact that smoking might have had in the pathogenesis of goiter, hyperthyroidism and autoimmune phenomena of GD and GO.

Role of smoking in goiter morphology and thyrotropin response to TRH in untreated goitrous women

Three groups of women were evaluated for TSH response to TRH and for goiter morphology by means of thyroid ultrasonography: group A = goitrous nonsmokers; group B1 = goitrous moderate-smokers; group B2 = goitrous heavy-smokers. They were compared with a control group (group C) made up nongoitrous, nonsmoking women. The size of the goiter was not correlated with the daily consumption of cigarettes, even though in heavy smokers a nodular goiter was prevalent as shown by ultrasonography. The serum values of TT3 showed significant differences between nonsmokers and heavy smokers (p less than (p less than 0.005), whereas the serum values of TT4 and of basal TSH showed no statistically significant differences. On the contrary, the TSH response to TRH showed a significant difference between heavy and nonsmokers (p less than 0.05). In conclusion, it has been demonstrated that goitrous cigarette heavy smokers show: i) A prevalence of statistically significant nodular goiter; ii) A significantly higher TT3 serum levels; iii) A significantly higher re-of TSH to TRH. These data suggest that cigarette smoking favors the development of nodular goiter and can involve the central regulation of the hypothalamus-pituitary-thyroid interaction.

Postpartum thyroid dysfunction in Mid Glamorgan

A high prevalence of postpartum thyroid dysfunction has been reported in several countries, but there have been no systematic studies of its prevalence in Britain. Among a group of 901 consecutive, unselected pregnant women thyroid autoantibodies were detected in 117 (13%) at booking. The clinical course of postpartum thyroid dysfunction, factors associated with its development, and its likely prevalence were defined in 100 of these women with thyroid antibodies and 120 women with no such antibodies who were matched for age. None of the women had a history of autoimmune thyroid disease. Normal reference ranges for thyroid function during pregnancy and post partum were established in the 120 women negative for thyroid antibodies. On the basis of these observations postpartum thyroid dysfunction was observed in 49 (22%) of the 220 women studied, and the prevalence in the total group of 901 women was estimated to be 16.7%. Thyroid dysfunction, mainly occurring in the first six months post partum, was usually transient and included both destruction induced hyperthyroidism and hypothyroidism. The development of the syndrome was significantly related to smoking more than 20 cigarettes a day and the presence of thyroid microsomal autoantibodies at booking. Of the 16 women with a family history of thyroid disease in whom thyroid microsomal autoantibody activity was detectable at booking, 11 developed thyroid dysfunction. Age, parity, presence of goitre at presentation, duration of breast feeding, and the sex and birth weight of the infant were not associated with the development of postpartum thyroid dysfunction. The mood changes experienced by women post partum may in part be associated with altered thyroid function during this time.

Influence of cigarette smoking on thyroid hormone levels

1 Serum triiodothyronine (T3), thyroxine (T4) and thyrotropin (TSH) concentrations and urinary thiocyanate levels were examined in healthy smokers and non-smokers as an indicator of smoking behaviour. Smokers were subdivided into moderate and heavy. 2 Significant differences in urinary thiocyanate levels were apparent between all three groups. For heavy smokers, serum T3 concentrations were significantly above the values found in non-smokers. Increased serum T3 levels were not accompanied by a substantial change in serum T4 and TSH concentrations.

Thyroglobulin in cord blood. The influence of the mode of delivery and the smoking habits of the mother

The cord thyroglobulin (Tg) concentration was estimated in 160 full-term newborns of whom 103 were delivered normally, 26 by elective Cesarean section and 31 by vacuum extraction. There was no correlation between the median cord Tg concentration and gestational age at delivery (37-43 weeks), birth weight or sex of the child or the median cord TSH concentration. The median cord Tg concentration was significantly higher in the children born by Cesarean section than in those delivered by vacuum extraction (P less than 0.001). The same tendency was found when smokers and non-smokers were compared separately. Mechanical force on the thyroid gland during labour and delivery therefore does not seem to increase the cord Tg concentration. The influence of maternal cigarette smoking on the cord Tg concentration was studied also. Forty-five mothers were smokers. The median cord Tg concentration in the children of these women was significantly higher than in the children of non-smoking mothers (130 micrograms/l vs 100 micrograms/l, P less than 0.001), whereas the median cord TSH concentration did not differ between these groups. It therefore seems possible that components of cigarette smoke, e.g. thiocyanate, may have a direct effect on the thyroid gland of the fetus.

High frequency of goitre in cigarette smokers

Thyroid function, the clinical occurrence of goitre and ultrasonically determined thyroid gland volume were investigated in 219 healthy subjects randomly chosen from hospital employees. Thirty-five subjects (16%) had a clinically detectable goitre. The frequency of goitre among smokers was higher (32 of 107, 30%) than among non-smokers (3 of 112, 3%), (P less than 0.001). Median thyroid volume was significantly higher in smokers, 26 ml (range 11-55 ml), compared with non-smokers, 15 ml (range 8-37 ml), (P less than 0.001). The median serum thyroglobulin levels were significantly higher and median serum thyrotropin levels lower in smokers compared with non-smokers. There were no differences between the groups regarding serum levels of T4, T3, rT3, free T4 index, free T3 index, thyroglobulin antibodies and 131I uptake (24 h) in the thyroid gland. It is suggested that these findings could partly be due to inhaled thiocyanate and/or increased adrenergic stimulation of the thyroid gland in smokers.

Thyroregulatory changes associated with smoking in 70-year-old men

In a previous study we have analysed serum free T4 concentrations in a representative population of 70-year-old men. In the present study the effect of previous or present tobacco smoking on free T4, T4, T3, rT3, TSH and thyroid hormone binding proteins was analysed in 181 of the 460 men, excluding those with past or present goitre, those who were obviously ill or had died between 70 and 75 years 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 also to differences in TBG levels. The results indicate that tobacco smoking is associated with long-term alterations in thyroregulatory function.