Small Differences in Thyroid Function May Be Important for Body Mass Index and the Occurrence of Obesity in the Population

Endocrine Unit, Medical Clinic I, Bispebjerg Hospital, Copenhagen, Denmark.
Journal of Clinical Endocrinology &amp Metabolism (Impact Factor: 6.21). 07/2005; 90(7):4019-24. DOI: 10.1210/jc.2004-2225
Source: PubMed


Increasing prevalence of overweight in the population is a major concern globally; and in the United States, nearly one third of adults were classified as obese at the end of the 20th century. Few data have been presented regarding an association between variations in thyroid function seen in the general population and body weight.
The aim of this study was to investigate the association between thyroid function and body mass index (BMI) or obesity in a normal population.
A cross-sectional population study (The DanThyr Study) was conducted.
In all, 4649 participants were investigated, and 4082 were eligible for these analyses after exclusion of subjects with previous or present overt thyroid dysfunction.
The study examined the association between category of serum TSH or serum thyroid hormones and BMI or obesity in multivariate models, adjusting for possible confounding.
We found a positive association between BMI and category of serum TSH (P < 0.001) and a negative association between BMI and category of serum free T(4) (P < 0.001). No association was found between BMI and serum free T(3) levels. The difference in BMI between the groups with the highest and lowest serum TSH levels was 1.9 kg/m(2), corresponding to a difference in body weight of 5.5 kg among women. Similarly, the category of serum TSH correlated positively with weight gain during 5 yr (P = 0.04), but no statistically significant association was found with weight gain during 6 months (P = 0.17). There was an association between obesity (BMI > 30 kg/m(2)) and serum TSH levels (P = 0.001).
Our results suggest that thyroid function (also within the normal range) could be one of several factors acting in concert to determine body weight in a population. Even slightly elevated serum TSH levels are associated with an increase in the occurrence of obesity.

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    • "Meta-analyses of population-based studies further confirm the existence of an association between subclinical hypothyroidism and CAD [5] [6] or cardiovascular mortality particularly among patients < 65 years of age [5] [7]. Evidence available also suggests that TSH levels in the upper part of reference range are associated with worse cardiovascular risk profile including endothelial dysfunction [8], reduced glomerular filtration rate [9], systolic and diastolic blood pressure [10], arterial stiffness [11], body mass index [12], metabolic syndrome [13] [14], less favorable lipid levels [15], coronary [16] or carotid [17] atherosclerosis and myocardial infarction [18]. Nevertheless the association between TSH level in the upper part of reference range and mortality remains debatable [19] [20] [21]. "
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    ABSTRACT: Thyroid-stimulating hormone (TSH) in the upper part of reference range is associated with cardio-metabolic disorders. The association of TSH within reference range with prognosis of patients with coronary artery disease (CAD) after percutaneous coronary intervention (PCI) remains poorly investigated. The study included 8010 consecutive patients with CAD who were treated with PCI. All patients had a TSH level within reference range (0.3 to 4.0mU/L). The primary outcome was 3-year all-cause mortality. TSH tertiles were: 1st tertile (0.3mU/L to <1.02mU/L; n=2694), 2nd tertile (1.02mU/L to <1.67mU/L; n=2654) and 3rd tertile (1.67mU/L to 4.00mU/L; n=2662). The primary outcome (3-year mortality) occurred in 753 patients: 240 deaths in the 1st, 227 deaths in the 2nd and 286 deaths in the 3rd TSH tertile (Kaplan-Meier estimates of mortality 10.2%, 9.8% and 12.3%; adjusted hazard ratio [HR]=1.31, 95% confidence interval [CI] 1.04-1.66 for each tertile increase). TSH level was associated with 30-day mortality (mortality estimates, 1.6% in the 1st, 1.6% in the 2nd and 3.5% in the 3rd TSH tertile; adjusted HR=2.30 [1.33-3.97] for each tertile increase) but not with 30-day to 3-year mortality (mortality estimates, 8.6% in the 1st, 8.2% in the 2nd and 8.8% in the 3rd TSH tertile; P=0.603). The incidence of cardiogenic shock or peri-PCI bleeding was increased in patients in the upper TSH tertile. In patients with CAD undergoing PCI, TSH level in the upper part of reference range was associated with increased risk of mortality after PCI. Copyright © 2015. Published by Elsevier Inc.
    Metabolism: clinical and experimental 07/2015; 64(10). DOI:10.1016/j.metabol.2015.07.009 · 3.89 Impact Factor
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    • "The increase in BMI may be due to the increased prevalence of subclinical hypothyroidism. A small elevation in TSH and an increase in BMI have been seen in other studies [30] [31]. Women with abnormal thyroid function had significantly higher BMI than women with normal thyroid function, both at baseline and in this follow-up. "
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    ABSTRACT: Thyroid dysfunction can be a result of excessive iodine intake, which may have adverse health consequences, particularly for women in fertile age. In 2010, we conducted a cross-sectional study among lactating women with excessive iodine intake in the Saharawi refugee camps in Algeria and found a high prevalence of thyroid dysfunction. Three years later, we conducted a follow-up study to monitor the iodine situation and explore whether thyroid dysfunction still was highly prevalent when the women no longer were post-partum. None of the women were treated for hyper- or hypothyroidism between baseline and follow-up. In 2013, we were able to recapture 78 of the 111 women from the baseline. Thyroid hormones and antibodies were measured in serum and thyroid size was assessed by palpation. Urinary iodine concentration (UIC) and drinking water iodine concentration were measured. The overall prevalence of thyroid dysfunction and/or positive antibodies was 34.3% and was not significantly changed from baseline. Of the non-pregnant women we reexamined, 17 had hypo- or hyperthyroidism in 2010; among these, 12 women still had abnormal thyroid function at follow-up. In addition, we found 9 new cases with marginally abnormal thyroid function. Women with thyroid dysfunction and/or positive antibodies had significantly higher BMI and thyroglobulin than women with normal thyroid function. We also found that women with high breast milk iodine concentration (BMIC) at baseline had more thyroid dysfunction at follow-up than the women with lower BMIC at baseline. At follow-up, the prevalence of thyroid dysfunction was still high and had not changed during the 3 years between studies and from a postpartum period. The women still had a high iodine intake indicated by high UIC. Breast milk iodine concentration from baseline predicted thyroid dysfunction at follow-up. Copyright © 2015 Elsevier GmbH. All rights reserved.
    Journal of Trace Elements in Medicine and Biology 03/2015; 31. DOI:10.1016/j.jtemb.2015.03.004 · 2.37 Impact Factor
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    • "This information was in response to general questions about medical conditions; questions specifically about thyroid disease were not asked. We examined the association of craniosynostosis with the following factors related to maternal thyroid dysfunction: maternal age, race-ethnicity, parity, pre-pregnancy body mass index (BMI), fertility medications or procedures (as a proxy for fertility problems), previous miscarriages , diabetes, hypertension, intake of anti-depressants (a proxy for depression) or iron-only supplements (a proxy for anemia), smoking, and alcohol consumption [Glinoer 1998; Hollowell et al., 2002; Belin et al., 2004; Knudsen et al., 2005; Zimmermann et al., 2007; Ashoor et al., 2010; Carle et al., 2012a; Carle et al., 2012b; De Groot et al., 2012; Wu et al., 2013]. "
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    ABSTRACT: Thyroid disease is a common problem among women of reproductive age but often goes undiagnosed. Maternal thyroid disease has been associated with increased risk of craniosynostosis. We hypothesized that known risk factors for thyroid disease would be associated with risk of craniosynostosis among women not diagnosed with thyroid disease. Analyses included mothers of 1,067 cases and 8,494 population-based controls who were interviewed for the National Birth Defects Prevention Study. We used multivariable logistic regression to estimate adjusted odds ratios (AOR) and 95% confidence intervals (CI). After excluding women with diagnosed thyroid disease, younger maternal age (AOR 0.7, 95% CI 0.6-0.9, for <25 years versus 25-29), black or other race-ethnicity (AOR 0.3, 95% CI 0.2-0.4 and AOR 0.6, 95% CI 0.4-0.8, respectively, relative to non-Hispanic whites), fertility medications or procedures (AOR 1.5, 95% CI 1.2-2.0), and alcohol consumption (AOR 0.8, 95% CI 0.7-0.9) were associated with risk of craniosynostosis, based on confidence intervals that excluded 1.0. These associations with craniosynostosis are consistent with the direction of their association with thyroid dysfunction (i.e., younger age, black race-ethnicity and alcohol consumption are associated with reduced risk and fertility problems are associated with increased risk of thyroid disease). This study thus provides support for the hypothesis that risk factors associated with thyroid dysfunction are also associated with risk of craniosynostosis. Improved understanding of the potential association between maternal thyroid function and craniosynostosis among offspring is important given that craniosynostosis carries significant morbidity and that thyroid disease is under-diagnosed and potentially modifiable. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
    American Journal of Medical Genetics Part A 02/2015; 167(4). DOI:10.1002/ajmg.a.36953 · 2.16 Impact Factor
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