Thyroid function in humans with morbid obesity

Dietary iodine absorption is not influenced by malabsorptive bariatric surgery

BACKGROUND

Bariatric surgery is accompanied by malabsorption of protein, carbohydrates, fats, vitamins, and trace elements. Iodine is essential to the synthesis of thyroid hormones. The aim of this study was to estimate the daily iodine intake in severely obese patients before and after bariatric surgery.

METHODS

Thirty-five severely obese patients (obese group) with a BMI of 51.3 ± 8.3 kg/m(2) were studied before, 3 months, and 6 months after bariatric surgery. Eleven out of 35 patients were subjected to gastric bypass operation Roux-en-Y and 24 were subjected to a variant of biliopancreatic diversion with long limb procedure. The patients did not use any iodine supplements and no iodine antiseptics were administered during the operation. The messmates of the patients, following a similar diet (control group) with a BMI of 31.2 ± 10.7 kg/m(2), were also studied. Serum T3, T4, TSH, thyroid peroxidase antibodies, urinary iodine excretion (UIE) in a spot urine, and thyroid volume were measured in all subjects, at baseline and at 3- and 6-month follow-up in the obese group.

RESULTS

UIE at baseline was similar in obese and control group (median (min-max), 129.5 (24.9-462) vs. 138.9 (30.8-381) μg/L, ns). In the obese group, a transient increase of UIE was observed 3 months after the operation and returned to baseline levels 6-months postsurgery.

CONCLUSIONS

The UIE is not reduced after malabsorptive bariatric surgery, although all stomach, duodenum, and a substantial part of jejunum were bypassed. It appears that iodine is absorbed sufficiently along the remaining gastrointestinal tract.

Thyroid disorders and gastrointestinal and liver dysfunction: A state of the art review

Thyroid disorders commonly impact on the gastrointestinal system and may even present with gastrointestinal symptoms in isolation; for example, metastatic medullary thyroid carcinoma typically presents with diarrhoea. Delays in identifying and treating the underlying thyroid dysfunction may lead to unnecessary investigations and treatment, with ongoing morbidity, and can potentially be life-threatening. Similarly, gastrointestinal diseases can impact on thyroid function tests, and an awareness of the concept and management of non-thyroidal illness is necessary to avoid giving unnecessary thyroid therapies that could potentially exacerbate the underlying gastrointestinal disease. Dual thyroid and gastrointestinal pathologies are also common, with presentations occurring concurrently or sequentially, the latter after a variable time lag that can even extend over decades. Such an association aetiologically relates to the autoimmune background of many thyroid disorders (e.g. Graves' disease and Hashimoto's thyroiditis) and gastrointestinal disorders (e.g. coeliac disease and inflammatory bowel disease); such autoimmune conditions can sometimes occur in the context of autoimmune polyglandular syndrome. Emphasis should also be given to the gastrointestinal side effects of some of the medications used for thyroid disease (e.g. anti-thyroid drugs causing hepatotoxicity) and vice versa (e.g. interferon therapy causing autoimmune thyroid dysfunction). In this review, we discuss disorders of the thyroid-gut axis and identify the evidence base behind the management of such disorders.

Laparoscopic sleeve gastrectomy leads to reduction in thyroxine requirement in morbidly obese patients with hypothyroidism

BACKGROUND

The impact of laparoscopic sleeve gastrectomy (LSG) on various co-morbidities including type II diabetes mellitus, hypertension, and sleep apnea is well established. However, its effect on hypothyroidism has not been given due attention evidenced by the scant literature on the subject. The purpose of this report is to assess the change in thyroxine (T4) requirement in morbidly obese patients with clinical hypothyroidism after LSG.

METHODS

We conducted a retrospective review of morbidly obese patients on T4 replacement therapy for clinical hypothyroidism who underwent LSG from August 2009 to July 2012 at our institution.

RESULTS

Of the 200 patients who underwent LSG during this period, 21 (10.5 %) were on T4 replacement therapy preoperatively for clinical hypothyroidism. Two patients were lost to follow-up. The remaining 19 patients were categorized into two groups. Group 1 comprised 13 patients with decreased T4 requirements after LSG. Group 2 comprised six patients in whom the T4 dose remained unaltered. The mean change in T4 requirement in group 1 was 42.07 % (12-100 %). Group 1 patients had a significantly higher mean preoperative body mass index (48.7 vs. 43.0 kg/m(2); p = 0.03) than the group 2 patients. There was a significant correlation between the percentage excess weight loss and the percentage change in T4 requirement in group 1 (r = 0.607, p = 0.028).

CONCLUSIONS

Sleeve gastrectomy has a favorable impact on hypothyroid status as seen by a reduction in T4 requirement in the majority of morbidly obese patients with overt hypothyroidism.

Laparoscopic sleeve gastrectomy leads to reduction in thyroxine requirement in morbidly obese patients with hypothyroidism

BACKGROUND

The impact of laparoscopic sleeve gastrectomy (LSG) on various co-morbidities including type II diabetes mellitus, hypertension, and sleep apnea is well established. However, its effect on hypothyroidism has not been given due attention evidenced by the scant literature on the subject. The purpose of this report is to assess the change in thyroxine (T4) requirement in morbidly obese patients with clinical hypothyroidism after LSG.

METHODS

We conducted a retrospective review of morbidly obese patients on T4 replacement therapy for clinical hypothyroidism who underwent LSG from August 2009 to July 2012 at our institution.

RESULTS

Of the 200 patients who underwent LSG during this period, 21 (10.5 %) were on T4 replacement therapy preoperatively for clinical hypothyroidism. Two patients were lost to follow-up. The remaining 19 patients were categorized into two groups. Group 1 comprised 13 patients with decreased T4 requirements after LSG. Group 2 comprised six patients in whom the T4 dose remained unaltered. The mean change in T4 requirement in group 1 was 42.07 % (12-100 %). Group 1 patients had a significantly higher mean preoperative body mass index (48.7 vs. 43.0 kg/m(2); p = 0.03) than the group 2 patients. There was a significant correlation between the percentage excess weight loss and the percentage change in T4 requirement in group 1 (r = 0.607, p = 0.028).

CONCLUSIONS

Sleeve gastrectomy has a favorable impact on hypothyroid status as seen by a reduction in T4 requirement in the majority of morbidly obese patients with overt hypothyroidism.

Indices of adiposity and thyroid hormones in euthyroid postmenopausal women

OBJECTIVE

We aimed to evaluate the association between thyroid hormones and indices of obesity in a sample of euthyroid postmenopausal women.

DESIGN

Cross-sectional study.

METHODS

Serum levels of TSH, free triiodothyronine (FT3), and free thyroxine (FT4) as well as BMI and waist:hip ratio (WHR) were evaluated in 194 healthy euthyroid postmenopausal women. Ultrasonography was used to assess abdominal fat layers (subcutaneous fat (SF), preperitoneal fat (PF), and SF:PF ratio). Indices of adiposity were defined as high vs low depending on the median value of the assessed parameters.

RESULTS

After multivariate adjustment for traditional risk factors, lower FT4 levels and a higher FT3:FT4 ratio predicted higher SF mass (FT4, Exp(β)=0.035, P=0.020 and FT3:FT4, Exp(β)=2.374, P=0.018), whereas higher FT3 predicted higher PF mass (Exp(β)=2.815, P=0.032). Women with FT3:FT4 above the highest quartile had a significantly higher SF mass as compared to women in the lowest quartile (1.81 ± 0.62 cm vs 1.54 ± 0.46 cm, P=0.027). BMI had a positive independent association with TSH (Exp(β)=1.829, P=0.018). Finally, FT3 was significantly associated with SF mass among women with higher BMI (FT3, β=0.259, P=0.040) and women with higher WHR (β=0.309, P=0.020) but not among women with lower BMI or WHR values.

CONCLUSION

Thyroid hormone levels, and in particular FT3, were independently associated with SF and PF in euthyroid postmenopausal women, and this association was mainly evident in women with higher BMIs. On the other hand, among traditional indices of adiposity, only TSH was positively associated with BMI. Larger prospective studies are needed to evaluate the significance of the present findings.

Thyroid Function in Pregnancy: What Is Normal?

BACKGROUND

Gestational thyroid dysfunction is common and associated with maternal and child morbidity and mortality. During pregnancy, profound changes in thyroid physiology occur, resulting in different thyroid-stimulating hormone (TSH) and free thyroxine (FT4) reference intervals compared to the nonpregnant state. Therefore, international guidelines recommend calculating trimester- and assay-specific reference intervals per center. If these reference intervals are unavailable, TSH reference intervals of 0.1–2.5 mU/L for the first trimester and 0.2–3.0 mU/L for the second trimester are recommended. In daily practice, most institutions do not calculate institution-specific reference intervals but rely on these fixed reference intervals for the diagnosis and treatment of thyroid disorders during pregnancy. However, the calculated reference intervals for several additional pregnancy cohorts have been published in the last few years and show substantial variation.

CONTENT

We provide a detailed overview of the available studies on thyroid function reference intervals during pregnancy, different factors that contribute to these reference intervals, and the maternal and child complications associated with only minor variations in thyroid function.

SUMMARY

There are large differences in thyroid function reference intervals between different populations of pregnant women. These differences can be explained by variations in assays as well as population-specific factors, such as ethnicity and body mass index. The importance of using correct reference intervals is underlined by the fact that even small subclinical variations in thyroid function have been associated with detrimental pregnancy outcomes, including low birth weight and pregnancy loss. It is therefore crucial that institutions do not rely on fixed universal cutoff concentrations, but calculate their own pregnancy-specific reference intervals.

Role of thyroid hormone homeostasis in obesity-prone and obesity-resistant mice fed a high-fat diet

BACKGROUND

The exact mechanism for different propensities to obesity when consuming a high-fat diet (HFD) is largely unknown. Thyroid hormone (TH) is an important modulator of energy homeostasis and body weight.

OBJECTIVE

The present study aimed to find the potential mechanisms of TH in the development of obesity-prone (OP) and obesity-resistant (OR) mice after short-term and long-term HFD feeding.

METHODS

C57Bl/6 male mice were randomly divided into two groups: a low-fat diet (LFD) group and an HFD group. In the 7th week, HFD-fed mice were classified as OP or OR according to upper and lower tertiles of body weight. Half of the mice were sacrificed at this time point and the remaining mice were kept on feeding and sacrificed in the 27th week. Indirect calorimetry was performed. At harvest, serum was used for ELISA assays and oxidative stress biomarkers determination. Tissues were dissected for deiodinases activity and relative mRNA expression determination, as well as antioxidant capacity evaluation.

RESULTS

In the 7th week, OP mice showed a significant body weight gain, decreased energy expenditure (EE), normal circulating TH levels, and activated HPT axis, whereas OR mice had normal body weight and maintained T(3) levels only through enhancing hepatic D1 activity. In the 27th week, OR mice gained more body weight than LFD mice accompanied by an activation of HPT axis and decreased hepatic deiodination. Genes involved in TH production were down-regulated in OP mice and up-regulated in OR mice. Changes in deiodinases activity and thyroid function were related with redox status in specific tissues. Furthermore, OP mice had more serious hepatic steatosis than OR mice, with up-regulation of T(3) target genes (e.g. Srebp1c, Acc1, Fasn) involved in lipid synthesis and down-regulation of Pgc1α, Cyp7a1 and Cpt1α.

CONCLUSIONS

HPT axis function and deiodinases activity might be involved in different propensities to obesity and the ability of OR mice to resist obesity was limited.

Thyroid hormonal status among children with obesity

BACKGROUND

It is presumed that free T4 and thyroid-stimulating hormone (TSH) levels are related to obesity, but the findings are inconsistent. In this study we evaluated T4 and TSH concentrations between normal children and those with obesity and possible correlations between body mass index (BMI) and these markers.

METHODS

In this prospective study, 190 children who were overweight and obese and 133 children without obesity of the same age and sex were evaluated. Thyroid function tests (TSH, total T4, free T4 and free T3) were measured in all subjects in both groups. Thyroid antibodies (thyroid peroxidase and thyroglobulin) were determined among those with elevated TSH levels.

RESULTS

Levels of TSH and total T4 were significantly higher in children with obesity compared with the control group. Subclinical hypothyroidism was significantly higher in children with obesity (14.7%) compared with normal subjects (6.8%, p = 0.02). Among children with obesity and increased TSH levels, 10.7% had positive thyroid peroxidase and thyroglobulin antibodies. There was significantly positive correlation between BMI z score and TSH level (r = 0.198, p < 0.001) and T4 level (r = 0.18, p = 0.001).

CONCLUSION

TSH and total T4 levels are increased in children who are overweight or obese and are a common finding in these children, but the incidence of thyroid antibodies is low in these patients and so could not be accounted for by thyroid autoimmunity. Due to these findings it is possible that increased TSH and total T4 levels are a consequence of obesity and could be reduced by decreasing BMI.

Prevalence of hypothyroidism in nonalcoholic fatty liver disease in patients attending a tertiary hospital in western India

The aim of this study was to assess the prevalence of hypothyroidism in patients with nonalcoholic fatty liver disease (NAFLD). The patients visiting Gastroenterology outpatient clinic between September 2011 and September 2013 at our tertiary care center were investigated for NAFLD. Three hundred controls were selected on the basis of negative ultrasound examination. All patients above 18 years were included. All patients with alcohol intake greater than 20 g/day, HBsAg or anti-HCV positivity, and history of liver disease were excluded. Full thyroid profile was carried out in all patients and they were classified as follows: subclinical hypothyroidism (TSH >5.5 IU/mL but <10 IU/mL) and overt hypothyroidism (TSH >10 IU/mL). Eight hundred (500 NAFLD and 300 controls) patients were studied. The mean age of NAFLD patients was 44.3 years and of controls was 41.6 years, respectively. The female-to-male ratio of NAFLD patients was 1.8:1 and of controls was 1.94:1, respectively (p>0.05). Hypothyroidism was significantly more common in NAFLD patients compared to controls. Eighty-four patients were detected to have hypothyroidism in NAFLD group compared to only four patients in control group (p<0.001). Mean ALT (55 vs. 21 IU), AST (44 vs. 18 IU), and BMI (29.17 vs. 25.14 kg/m2) were significantly higher in NAFLD hypothyroid group compared to nonhypothyroid NAFLD. Multivariate regression analysis showed that NAFLD was statistically significantly associated with hypothyroidism [odds ratio (OR) 14.94, 95 % confidence interval (CI), 3.5 to 62.6]. Steatohepatitis was more common in hypothyroid as compared to nonhypothyroid group [OR 3.9, 1.2 to 11.1 (95 % CI)]. The prevalence of hypothyroidism in NAFLD was 16.8 %. Hypothyroidism was closely associated with NAFLD independently of known metabolic risk factors, confirming a significant clinical relationship between these two diseases.

Free Triiodothyronine Levels Are Associated with Diabetic Nephropathy in Euthyroid Patients with Type 2 Diabetes

Objective. To investigate the association of thyroid function and diabetic nephropathy (DN) in euthyroid patients with type 2 diabetes. Methods. A total of 421 patients were included in this cross-sectional study. The following parameters were assessed: anthropometric measurements, fast plasma glucose, serum creatinine, lipid profile, HbA1c, free triiodothyronine (FT3), free thyroxine, thyroid-stimulating hormone levels, and urinary albumin-to-creatinine ratio (UACR). Patients with UACR of ≥30 mg/g were defined as those suffering from DN. Results. Of the 421 patients, 203 (48.2%) suffered from DN, and no difference was found between males and females. The patients with DN yielded significantly lower FT3 levels than those without DN (P < 0.01). The prevalence of DN showed a significantly decreasing trend across the three tertiles based on FT3 levels (59.6%, 46.4%, and 38.6%, P < 0.01). After adjustment for gender and age, FT3 levels were found to correlate positively with estimated glomerular filtration rate (P = 0.03) and negatively with UACR (P < 0.01). Multiple linear regression analysis showed that FT3 level was independently associated with UACR (β = -0.18, t = -3.70, and P < 0.01). Conclusion. Serum FT3 levels are inversely associated with DN in euthyroid patients with type 2 diabetes, independent of traditional risk factors.

Isolated Subclinical Hyperthyrotropinemia in Obese Children: Does Levothyroxine (LT4) Improve Weight Reduction during Combined Behavioral Therapy?

Objective. The study aim was to analyze whether anthropometrical parameters and TSH values in obese children with isolated subclinical hypothyroidism (IsHT) treated with levothyroxine (LT4) and weight reduction program differ from those managed by dietary and behavior counselling only. Material and Methods. 51 obese children with IsHT, who were treated according to the same weight reduction program, were retrospectively analyzed. They were divided into two groups: Group 1, n = 26, and Group 2, n = 25, without or with LT4 therapy, respectively. Changes in anthropometrical (delta BMI z-score) and hormonal (delta TSH) status were analyzed at the first follow-up visit. Results. In both groups significant decrease of TSH and BMI z-score values were noted. TSH normalized in 80.9% of children from Group 1 versus 90.5% from Group 2, p = NS. Delta BMI z-score was insignificantly higher in Group 1 compared to Group 2. Delta TSH was significantly related to initial TSH level in children treated by lifestyle intervention program only. Conclusions. In obese children with sHT dietary-behavioral management intervention contributed to reduction of body mass index, irrespective of levothyroxine use. This finding suggests that moderately elevated levels of TSH are a consequence rather than cause of overweight and pharmacological treatment should be avoided.

Therapeutic phytogenic compounds for obesity and diabetes

Natural compounds have been used to develop drugs for many decades. Vast diversities and minimum side effects make natural compounds a good source for drug development. However, the composition and concentrations of natural compounds can vary. Despite this inconsistency, half of the Food and Drug Administration (FDA)-approved pharmaceuticals are natural compounds or their derivatives. Therefore, it is essential to continuously investigate natural compounds as sources of new pharmaceuticals. This review provides comprehensive information and analysis on natural compounds from plants (phytogenic compounds) that may serve as anti-obesity and/or anti-diabetes therapeutics. Our growing understanding and further exploration of the mechanisms of action of the phytogenic compounds may afford opportunities for development of therapeutic interventions in metabolic diseases.

Obesity with and without metabolic syndrome: do vitamin D and thyroid autoimmunity have a role?

AIMS

To investigate serum levels of thyroid stimulating hormone (TSH), anti-thyroid peroxidase antibody (TPO), and 25(OH)D in the presence or absence of metabolic syndrome in an obese population.

METHODS

Data from a prospectively generated "Obesity Polyclinic" database that includes socio-demographic characteristics, anthropometric, and laboratory measurements of obese subjects were retrospectively analyzed. Subjects with body-mass index (BMI) ≥30kg/m(2) were eligible. After detailed analysis and exclusion of unavailable cases, subjects diagnosed with and without metabolic syndrome were compared for TSH, anti-TPO, and 25(OH)D.

RESULTS

Of the study participants (n=548; men/women, 64/484), 277 were diagnosed with metabolic syndrome [Met-S (+)]. Met-S (+) patients had a higher mean BMI (36.4 vs. 32.3kg/m(2), p<.001) and percentage body fat (PBF) (39.2 vs. 35.3%, p<.001), but similar TSH (2.1 vs. 2.2mIU/mL, p=.759), anti-TPO (12 vs. 13IU/mL, p=.483), 25(OH)D (13.2 vs. 12.6ng/mL, p=.409), and calcium-phosphorus product (28.7 vs. 29.5mg/dL, p=0.275), compared to Met-S (-) subjects. When serum TSH, anti-TPO, and 25(OH)D levels were analyzed according to tertiles for comparisons of fasting plasma glucose, triglycerides, high-density lipoprotein cholesterol, BMI, and PBF, only 25(OH)D levels were negatively correlated with BMI and PBF.

CONCLUSIONS

Although decreased 25(OH)D levels were related to the degree of obesity in obese subjects, serum 25(OH)D levels per se did not seem to be associated with metabolic syndrome. The prevalence of thyroid autoimmunity and hypothyroidism were high in this obese sample; however, neither serum TSH nor anti-TPO levels correlated with metabolic syndrome. Our findings did not support the hypothesis that thyroid autoimmunity and/or vitamin D status have a role in the development of metabolic disturbances in the obese population.

Mechanisms in endocrinology: the crosstalk between thyroid gland and adipose tissue: signal integration in health and disease

Obesity and thyroid diseases are common disorders in the general population and they frequently occur in single individuals. Alongside a chance association, a direct relationship between 'thyroid and obesity' has been hypothesized. Thyroid hormone is an important determinant of energy expenditure and contributes to appetite regulation, while hormones and cytokines from the adipose tissue act on the CNS to inform on the quantity of energy stores. A continuous interaction between the thyroid hormone and regulatory mechanisms localized in adipose tissue and brain is important for human body weight control and maintenance of optimal energy balance. Whether obesity has a pathogenic role in thyroid disease remains largely a matter of investigation. This review highlights the complexity in the identification of thyroid hormone deficiency in obese patients. Regardless of the importance of treating subclinical and overt hypothyroidism, at present there is no evidence to recommend pharmacological correction of the isolated hyperthyrotropinemia often encountered in obese patients. While thyroid hormones are not indicated as anti-obesity drugs, preclinical studies suggest that thyromimetic drugs, by targeting selected receptors, might be useful in the treatment of obesity and dyslipidemia.

Brown adipose tissue in the treatment of obesity and diabetes: Are we hot enough?

The identification of functional brown adipose tissue in human adults has intensified interest in exploiting thermogenic energy expenditure for the purpose of weight management. However, food intake and energy expenditure are tightly regulated and it is generally accepted that variation in one component results in compensatory changes in the other. In the context of weight loss, additional biological adaptations occur in an attempt to further limit weight loss. In the present review, we discuss the relationship between increasing energy expenditure and body weight in humans, including the effects of cold exposure. The data raise the possibility that some processes, particularly those involved in thermogenesis, induce less compensatory food intake for a given magnitude of additional energy expenditure, a state we term the ‘thermogenic disconnect’. Although cold exposure increases thermogenesis and can putatively be exploited to induce weight loss, there are multiple adaptive responses to cold, of which many actually reduce energy expenditure. In order to optimally exploit either cold itself or agents that mimic cold for thermogenic energy expenditure, these non‐thermogenic cold responses must be considered. Finally, the relative contribution of brown adipose tissue vs other thermogenic processes in humans remains to be defined. However, overall the data suggest that activation of cold‐induced thermogenic processes are promising targets for interventions to treat obesity and its secondary metabolic complications. (J Diabetes Invest, doi:10.1111/j.2040‐1124.2011.00158.x, 2011)

Association between thyroid hormones and body fat in euthyroid subjects

OBJECTIVE

Thyroid hormones disorders are associated with changes of body composition. However, the relationship between thyroid hormones and body fat in a euthyroid population is unclear. The aim of this study was to explore the association between thyroid hormones and body fat in a euthyriod population.

SUBJECTS

A total of 865 euthyroid individuals were recruited in this study. Subjects with thyroid diseases or diabetes and who were taking medications that could influence thyroid hormones, weight or glucose metabolism were excluded.

MEASUREMENTS

FT3, FT4, lipid parameters, fasting insulin (FINS) and blood glucose were determined, and homeostasis model assessment for insulin resistance (HOMA-IR) was calculated. Anthropometric measurements were taken, and body fat parameters were assessed.

RESULTS

Serum FT3 was slightly higher in body mass index (BMI) ≥25 kg/m(2) group than that in BMI <25 kg/m(2) group (P < 0·05). However, the difference was too small to have clinical significance. FT4 levels were not significantly different between the two groups. Body weight, BMI, waist circumference, hip circumference, waist-to-hip ratio (WHR), percentage of body fat (PBF), waist-fat-to-hip-fat ratio, FINS and HOMA-IR increased linearly with the elevation of FT3 adjusted for age and gender. A multivariate linear regression analysis revealed that fat mass, PBF, HOMA-IR and FT4 contributed significantly to FT3 levels.

CONCLUSION

Grouped according to BMI, overweight and obese subjects have similar thyroid hormones compared to those with normal weight. Body composition parameters increase with the elevation of FT3, and FT3 is associated with body fat parameters in euthyroid subjects.

The prevalence of thyroid nodules and its relationship with metabolic parameters in a Chinese community-based population aged over 40 years

To investigate the prevalence of thyroid nodules (TN) among a community population aged >40 years and to explore the association between TN and its metabolic risk factors. Data from 9,533 adults aged over 40 years who participated in the epidemiological investigation of thyroid nodules in a Chinese community-based population from June to December 2011 were included in the analyses. We compared the levels of metabolic indices between the TN group and healthy controls. The prevalence of TN was 46.6% (39.7%, men; 50.3%, women) and it increased significantly with increasing age (P < 0.001). It was significantly higher in the group with hypertension than in that with normotension (P < 0.001) and was 43.0% in the normal blood glucose group, 49.4% in the prediabetes group, and 50.9% in the diabetes group (P < 0.001). Logistic regression analysis indicated that hypertension [odds ratio (OR) = 1.121 (1.025-1.225)] as well as prediabetes and diabetes [OR = 1.130 (1.036-1.233)] were all independent risk factors for TN after adjustment for sex, age, body mass index, blood lipid levels, smoking status, and alcohol consumption. The elderly population had a high prevalence of TN. Hypertension as well as prediabetes and diabetes might be independent risk factors for TN.

Effects of five-year treatment with testosterone undecanoate on metabolic and hormonal parameters in ageing men with metabolic syndrome

Metabolic and hormonal modifications after long-term testosterone (T) treatment have never been investigated. 20 hypogonadal men (mean T = 241 ng/dL-8.3 nmol/L) with metabolic syndrome (MS, mean age 58) were treated with T-undecanoate injections every 12 weeks for 60 months. 20 matched subjects in whom T was unaccepted or contraindicated served as controls. Primary endpoints were variations from baseline of metabolic and hormonal parameters. In T-group, significant reductions in waist circumference (-9.6 ± 3.8 cm, P < 0.0001), body weight (-15 ± 2.8 Kg, P < 0.0001), and glycosylated hemoglobin (-1.6  ±  0.5%, P < 0.0001) occurred, along with improvements in insulin sensitivity (HOMA-I; -2.8  ±  0.6, P < 0.0001), lipid profile (total/HDL-cholesterol ratio -2.9 ± 1.5, P < 0.0001), systolic and diastolic blood pressure (-23 ± 10 and -16 ± 8 mm Hg, P < 0.0001, resp.), and neck and lumbar T-scores (+0.5 ± 0.15 gr/cm(2), P < 0.0001; +0.7 ± 0.8, P < 0.0001, resp.). Also, serum vitamin D (+14.0 ± 1.3 ng/mL, P < 0.01), TSH (- 0.9 ± 0.3 mUI/mL, P < 0.01), GH (0.74 ± 0.2 ng/mL, P < 0.0001), and IGF1 (105 ± 11 ng/mL, P < 0.01) levels changed in T-group but not in controls. Normalization of T levels in men with MS improved obesity, glycemic control, blood pressure, lipid profile, and bone mineral density compared with controls. Amelioration in hormonal parameters, that is, vitamin D, growth hormone, and thyrotropin plasma levels, were reported.

Raised serum TSH in morbid-obese and non-obese patients: effect on the circulating lipid profile

Morbid obesity is associated with a high rate of raised serum TSH associated with normal free thyroid hormones. The body repercussions of this thyroid abnormality, suggesting subclinical hypothyroidism, are still debated. In particular, it is unclear whether the raised serum TSH of obesity results in changes of circulating lipids typically observed in hypothyroidism. Aim of this study was to evaluate the impact of a raised serum TSH on the lipid profile in morbid-obese and non-obese patients. Serum TSH, FT4, FT3, Tg-Ab, TPO-Ab and lipids were measured in 55 morbid-obese (BMI > 40 kg/m(2)) and 55 non-obese (BMI < 30 kg/m(2)) patients with a raised serum TSH. Despite similar serum levels of TSH, FT4 and FT3, morbid-obese patients displayed significantly lower mean levels of total cholesterol (200.8 ± 35.6 vs. 226.9 ± 41.4 mg/dl, p < 0.001) and a significantly lower prevalence of hypercholesterolemia (50.9 vs. 72.7 %, p < 0.01) when compared with non-obese patients. Morbid-obese patients also had lower mean serum HDL cholesterol and higher serum triglycerides. The impact of a raised serum TSH on the lipid profile differs in morbid-obese compared to non-obese patients, suggesting that obese patients might not be truly hypothyroid. Measuring total cholesterol could be a helpful tool for deciding whether a morbid-obese patient with a raised serum TSH should be given levothyroxine treatment.

Are plasma thyroid-stimulating hormone levels associated with degree of obesity and metabolic syndrome in euthyroid obese patients? A Turkish cohort study

We aimed to observe the association between degree of obesity and metabolic syndrome and plasma thyrotropin levels in obese, euthyroid Turkish patients. 947 obese and overweight patients who admitted to our outpatient clinic were assessed retrospectively. 150 healthy euthyroid cases were also recruited as the control group. Cases with metabolic syndrome were determined. Patients were divided into various subgroups as overweight, obese, morbid obese, men, and women. No statistical significance was determined when all the patients' and subgroups' plasma thyrotropin levels were compared to normal weight control group. No association was shown between the presence of metabolic syndrome and plasma thyrotropin levels for both all patients and subgroups. Also there was not any association between each component of metabolic syndrome and plasma thyrotropin levels. In conclusion, we did not found any significant association between plasma thyrotropin levels and obesity and metabolic syndrome in our euthyroid subjects.

Relationship between thyroid nodules and non-functioning adrenal incidentalomas and their association with insulin resistance

OBJECTIVE

The relationship between insulin resistance and thyroid nodules in patients with non-functional adrenal incidentalomas (AI) is not clearly understood. The aim of this study was to determine the frequency of thyroid nodules in AI patients, as well as to evaluate any possible associations with disorders of insulin resistance.

METHODS

Patients diagnosed with a non-functional AI were approached for inclusion in the study. Insulin resistance was evaluated using homeostasis model assessment (HOMA-IR). All participants were screened for the presence of thyroid nodule by ultrasonography, and fine needle aspiration biopsies were obtained from consenting subjects.

RESULTS

One-hundred-thirteen patients with AI and 152 age-, BMI- and gender-matched healthy controls were enrolled. AI patients had higher waist circumference and waist/hip ratio than the control group. Metabolic syndrome, hypertension and type 2 diabetes mellitus rates were significantly higher in AI patients. HOMA-IR was similar between the groups. At least one thyroid nodule was observed in 42 (27.6%) of the controls compared to 55 (48.7%) of AI patients (p < 0.001). The mean number of thyroid nodules in AI patients was significantly higher than the control subjects (2.4 ± 0.9 versus 1.7 ± 1.0, p = 0.008). Mean nodule volume was similar between AI patients and the controls. A correlation could not be established between adrenal tumor/thyroid nodule volumes and the number of thyroid nodules, HOMA-IR, waist circumference, waist/hip ratio, BMI and thyroid function tests.

CONCLUSION

A higher prevalence of thyroid nodule and a higher number of thyroid nodules were determined in patients with AI compared to healthy controls.

Moderate weight loss is sufficient to affect thyroid hormone homeostasis and inhibit its peripheral conversion

BACKGROUND

Thyroid hormones are important determinants of energy expenditure, and in rodents, adipose tissue affects thyroid hormone homeostasis via leptin signaling. The relationship between thyroid hormones and nutritional status in humans has been assessed primarily in drastic dietary or bariatric surgery interventions, while limited information is available on serial assessment of this axis during moderate, prolonged dietary restriction.

METHODS

To evaluate the effects of moderate dietary restriction on thyroid hormone homeostasis, 47 subjects with a body mass index (BMI) of 25-45 kg/m(2) were enrolled in a longitudinal intervention study; 30 nonoverweight volunteers were also enrolled as controls. Overweight and obese subjects underwent a 12-month individualized dietary intervention aimed at achieving a 5-10% weight loss.

RESULTS

The intervention resulted in a 6.3±0.9 kg (6.5±1.0%) weight loss. At baseline, thyrotropin (TSH) and T3 concentrations correlated significantly with fat mass (R=0.257, p=0.024 and R=0.318, p=0.005, respectively). After weight loss, T3 decreased significantly (from 112.7±3.1 to 101.8±2.6 ng/dL, p<0.001) in the absence of significant changes in TSH or free T4 (fT4). The decrease in serum T3 correlated with the decrease in weight (R=0.294, p<0.001). The T3:fT4 ratio decreased significantly (p=0.02) in individuals who lost >5% body weight.

CONCLUSIONS

T3 concentration closely correlates with individual nutritional status, and moderate weight loss results in a decrease in T3 with minimal changes in other thyroid hormone homeostasis parameters. The data suggest that a decrease in peripheral conversion of the prohormone T4 into its hormonally active metabolite T3 is at least in part responsible for the observed changes in thyroid hormone homeostasis.

Obesity and thyroid cancer: epidemiologic associations and underlying mechanisms

The incidence of thyroid cancer has been rising over the past few decades along with a parallel increase in obesity. Observational studies have provided evidence for a potential association between the two. By contrast, clinical data for a link between type 2 diabetes mellitus, a condition strongly associated with obesity, and thyroid cancer are limited and largely not supportive of such an association. Obesity leads to hypoadiponectinemia, a pro-inflammatory state, and insulin resistance, which, in turn, leads to high circulating insulin and insulin-like growth factor-1 levels, thereby possibly increasing the risk for thyroid cancer. Thus, insulin resistance possibly plays a pivotal role in underlying the observed association between obesity and thyroid cancer, potentially leading to the development and/or progression of thyroid cancer, through its interconnections with other factors including insulin-like growth factor-1, adipocytokines/cytokines and thyroid-stimulating hormone. In this review, epidemiological and clinical evidence and potential mechanisms underlying the proposed association between obesity and thyroid cancer risk are reviewed. If the association between obesity and thyroid cancer demonstrated in observational studies proves to be causal, targeting obesity (and/or downstream mediators of risk) could be of importance in the prevention and management of thyroid cancer.

Vegan diets and hypothyroidism

Diets eliminating animal products have rarely been associated with hypothyroidism but may protect against autoimmune disease. Thus, we investigated whether risk of hypothyroidism was associated with vegetarian compared to omnivorous dietary patterns. The Adventist Health Study-2 was conducted among church members in North America who provided data in a self-administered questionnaire. Hypothyroidism was queried at baseline in 2002 and at follow-up to 2008. Diet was examined as a determinant of prevalent (n = 4237 of 65,981 [6.4%]) and incident cases (1184 of 41,212 [2.9%]) in multivariate logistic regression models, controlled for demographics and salt use. In the prevalence study, in addition to demographic characterstics, overweight and obesity increased the odds (OR 1.32, 95% CI: 1.22–1.42 and 1.78, 95% CI: 1.64–1.93, respectively). Vegan versus omnivorous diets tended to be associated with reduced risk (OR 0.89, 95% CI: 0.78–1.01, not statistically significant) while a lacto-ovo diet was associated with increased risk (OR 1.09, 95% CI: 1.01–1.18). In the incidence study, female gender, white ethnicity, higher education and BMI were predictors of hypothyroidism. Following a vegan diet tended to be protective (OR 0.78, 95% CI: 0.59–1.03, not statistically significant). In conclusion, a vegan diet tended to be associated with lower, not higher, risk of hypothyroid disease.

Roux-en-Y gastric bypass and calorie restriction induce comparable time-dependent effects on thyroid hormone function tests in obese female subjects

OBJECTIVE

Obesity and weight loss influence thyroid hormone physiology. The effects of weight loss by calorie restriction vs Roux-en-Y gastric bypass (RYGB) in obese subjects have not been studied in parallel. We hypothesized that differences in transient systemic inflammation and catabolic state between the intervention types could lead to differential effects on thyroid hormone physiology.

DESIGN AND METHODS

We recruited 12 lean and 27 obese females with normal fasting glucose (normal glucose tolerant (NGT)) and 27 obese females with type 2 diabetes mellitus (T2DM) for this study. Weight loss was achieved by restrictive treatment (gastric banding or high-protein-low-calorie diet) or by RYGB. Fasting serum leptin, TSH, triiodothyronine (T₃), reverse T₃ (rT₃), and free thyroxine (fT₄) concentrations were measured at baseline and 3 weeks and 3 months after the start of the interventions.

RESULTS

Obesity was associated with higher TSH, T₃, and rT₃ levels and normal fT₄ levels in all the subjects when compared with the controls. After 3 weeks, calorie restriction and RYGB induced a decline in TSH levels and a rise in rT₃ and fT₄ levels. The increase in rT₃ levels correlated with serum interleukin 8 (IL8) and IL6 levels. After 3 months, fT₄ and rT₃ levels returned to baseline levels, whereas TSH and T₃ levels were persistently decreased when compared with baseline levels. No differences in the effects on thyroid hormone parameters between the interventions or between NGT and T2DM subjects were observed at any time point.

CONCLUSIONS

In summary, weight loss directly influences thyroid hormone regulation, independently of the weight loss strategy used. The effects may be explained by a combination of decreased leptin levels and transient changes in peripheral thyroid hormone metabolism.

Impact of body mass index on thyroid functions in Indian children

OBJECTIVE

There is controversy about the relation of thyroid functions and body mass index. The present study was aimed to assess the relationship between thyroid function and body mass index in Indian school children.

DESIGN

Population survey.

PATIENTS

Data were collected from 25 schools in 19 cities across five different geographical zones of India. Children, who consented, were evaluated for anthropometry and blood tests. Children were categorized as overweight and obese based on standard BMI criteria.

MEASUREMENTS

Serum samples were analysed for free T3, free T4, TSH and anti-TPO antibodies.

RESULTS

A total of 13,691 children in the age group of 5-18 years formed the study population. The mean age and mean BMI were 11·9 ± 3·0 years and 18·48 ± 3·89 kg/m² respectively. Among these, 2119 (15·5%) children were overweight and 536 (3·9%) were obese. Subclinical hypothyroidism was present in 943 (6·9%) children.FT3 and TSH levels increased and FT4 levels decreased with increasing BMI in euthyroid boys and girls. Prevalence of SCH was significantly higher in obese/overweight children (9·0%, vs 6·5%; P = 0·034) as compared with normal BMI children.

CONCLUSIONS

Serum FT3 and TSH were positively while FT4 was negatively associated with BMI in apparently healthy euthyroid children.

Is autoimmune thyroiditis a risk factor for early atherosclerosis in premenopausal women even if in euthyroid status?

Autoimmune thyroiditis (AIT) is a systemic disease. It is well-known that overt thyroid dysfunction is a cardiovascular risk factor. However, the influence of euthyroid status is unclear. The aim of this study was to evaluate the metabolic parameters and carotid intima-media thickness (CIMT) in euthyroid premenopausal women with AIT. Fourty-eight premenopausal women and 18 age-matched healthy controls attending the Endocrinology and Metabolism Clinic from 2008 to 2009 were enrolled to this cross-sectional study. Patients were divided into 2 groups according to TSH levels; patients in group 1 (n = 23) had TSH levels ≤ 2.5 μIU/mL and patients in group 2 had TSH levels > 2.5 μIU/mL (n = 25). All participants were evaluated by ultrasound for CIMT (mean of three segments in both carotid arteries) by the same experienced investigator. Fasting venous blood samples were collected to evaluate insulin resistance (HOMA-IR), TSH, FT4, plasma lipids, high-sensitive CRP (Hs-CRP), homocysteine, and fibrinogen. Carotid intima-media thickness was found to be significantly higher in patients than the controls (p < 0.001). However, there was no significant difference in average CIMT between group 1 and 2 (0.66 ± 0.08 vs 0.63 ± 0.09 mm). Anti-Tg levels were independently associated with CIMT in the patient group (p = 0.014). There were no significant correlations between serum TSH levels and BMI; waist circumference, serum lipids, and glucose levels. However, there was a positive significant correlation between TSH levels and blood pressure in the patients (for systolic blood pressure r = 0.466, p = 0.001, for diastolic blood pressure r = 0.372, p = 0.009). In the present study, it was shown that CIMT is increased in euthyroid premenopausal women with autoimmune thyroiditis compared to age-matched healthy controls.

Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association

OBJECTIVE

Hypothyroidism has multiple etiologies and manifestations. Appropriate treatment requires an accurate diagnosis and is influenced by coexisting medical conditions. This paper describes evidence-based clinical guidelines for the clinical management of hypothyroidism in ambulatory patients.

METHODS

The development of these guidelines was commissioned by the American Association of Clinical Endocrinologists (AACE) in association with American Thyroid Association (ATA). AACE and the ATA assembled a task force of expert clinicians who authored this article. The authors examined relevant literature and took an evidence-based medicine approach that incorporated their knowledge and experience to develop a series of specific recommendations and the rationale for these recommendations. The strength of the recommendations and the quality of evidence supporting each was rated according to the approach outlined in the American Association of Clinical Endocrinologists Protocol for Standardized Production of Clinical Guidelines-2010 update.

RESULTS

Topics addressed include the etiology, epidemiology, clinical and laboratory evaluation, management, and consequences of hypothyroidism. Screening, treatment of subclinical hypothyroidism, pregnancy, and areas for future research are also covered.

CONCLUSIONS

Fifty-two evidence-based recommendations and subrecommendations were developed to aid in the care of patients with hypothyroidism and to share what the authors believe is current, rational, and optimal medical practice for the diagnosis and care of hypothyroidism. A serum thyrotropin is the single best screening test for primary thyroid dysfunction for the vast majority of outpatient clinical situations. The standard treatment is replacement with L-thyroxine. The decision to treat subclinical hypothyroidism when the serum thyrotropin is less than 10 mIU/L should be tailored to the individual patient.

The interconnections between obesity, thyroid function, and autoimmunity: the multifold role of leptin

BACKGROUND

There is increasing evidence that changes in thyroid function are associated with obesity, a condition associated with a chronic low-grade state of inflammation. Meanwhile, recent data have disclosed a relation between obesity and thyroid autoimmunity, with the adipocyte hormone leptin appearing to be the key factor linking these two conditions.

SUMMARY

Leptin has variably been implicated in thyroid function, while recent findings suggest that leptin resistance may mitigate leptin deficiency and enhance autoimmunity in obese subjects via mechanisms operating independently of thyroid function. The development of resistance to the weight-lowering effects of leptin in obesity might well be initiated by activation of inflammatory signaling, which substantially contributes to the derangement of immune response and propagation of autoimmunity in susceptible individuals.

CONCLUSIONS

Regulation of inflammasome-derived cytokines in obesity is an important step in controlling the trigger of thyroid autoimmunity. The clarification of the pathways may offer innovative therapeutic targets in obesity and thyroid autoimmunity.

Associations between thyroid hormone levels and regional fat accumulation in euthyroid men

OBJECTIVE

Body adiposity, especially ectopic fat accumulation, has a range of metabolic and cardiovascular effects. This study aimed to investigate whether thyroid function is associated with various regional fat quantities in euthyroid subjects.

METHODS

A total of 100 euthyroid men (free triiodothyronine (fT3), 4.77±1.21 pg/ml; free thyroxine (fT4), 1.38±0.21 ng/dl; and TSH, 2.09±0.91 μIU/ml) were enrolled in this cross-sectional study. We measured accumulated regional fat using 64-slice multi-detector computed tomography. Multiple linear regression analysis was used to determine whether accumulated fat in each region was associated with clinical parameters after adjusting for age.

RESULTS

FT3 was inversely correlated with BMI (R=0.232, P=0.029) and LDL cholesterol level (R=0.277, P=0.019). FT4 was inversely correlated with waist circumference (R=0.350, P=0.008) and BMI (R=0.355, P0.001). In multiple linear regression analysis, fT3 and fT4 levels were significantly associated with pericardial fat volume (fT3: B=-0.079, 95% CI -0.142 to -0.017, P=0.013; fT4: B=-0.411, 95% CI -0.780 to -0.042, P=0.030) in euthyroid men, independent of age. FT3 level was inversely associated with intramuscular fat area (B=-0.059, 95% CI -0.106 to -0.011, P=0.016) and hepatic fat quantity (B=-0.237, 95% CI -0.441 to -0.033, P=0.024) in euthyroid men, independent of age.

CONCLUSIONS

In euthyroid men, low levels of fT3 and fT4 were significantly associated with increased pericardial fat volume and BMI.

Prevalence of goiter and thyroid nodular disease in patients with class III obesity

OBJECTIVES: To evaluate the prevalence of goiter and nodular disease in patients with class III obesity, and to correlate results with serum leptin levels and insulin resistance (IR) parameters. SUBJECTS AND METHODS: A cross-sectional study was performed to assess thyroid ultrasound (US) patterns, HOMA-IR, serum leptin, and TSH levels in obese patients and controls. RESULTS: Thyroid volume was positively correlated with body mass index (BMI) (r = 0.240, p = 0.039) and with HOMA-IR (r = 0.329; p < 0.01). Thyroid US patterns were similar between groups. However, when data from the male group was considered, greater thyroid volume was detected in the obese group compared with controls (10.8 vs. 8.5 cm³; p = 0.04). Also, nodules were more frequently detected (67% vs. 18%), as were nodules requiring FNAB (33.3% vs. 0%, p ≥ 0.05-0.09), in this group. CONCLUSION: Although IR did not correlate directly with the presence of nodules, the results support the hypothesis of a direct association between insulin resistance and thyroid volume.

Relationship of thyroid function with obesity and type 2 diabetes in euthyroid Tunisian subjects

OBJECTIVES

Although a relationship between obesity and metabolic consequences with thyroid function has been reported, the underlying pathogenesis is not completely known. In the current study, we evaluated the thyroid function in obese and/or diabetic patients compared to healthy normal weight peers, exploring the possible association between components of metabolic syndrome and thyroid function parameters.

METHODS

We recruited 108 subjects (56 male and 52 female). In all subjects, thyroid stimulating hormone (TSH), free thyroxine (FT4), fasting plasma levels of insulin and glucose, homeostasis model assessment for insulin resistance, and obesity parameters were assessed.

RESULTS

We found that circulating levels of TSH and FT4 were significantly increased in overweight and obese subjects. However, the data do not reveal any change of these hormones in diabetics. Multivariate linear regression analysis showed that TSH was directly associated with both obesity and insulin resistance parameters (p < 0.05). FT4 was negatively associated only with obesity parameters (p < 0.05).

CONCLUSIONS

Our data strongly support that the changes of thyroid hormones may be influenced by adiposity and its metabolic consequences, such as insulin resistance. This relationship can be explained by a cross talk between adipose tissue release and thyroid function. Nevertheless, metformin treatment seems to affect thyroid function in diabetic patients by maintaining plasma thyrotropin levels to subnormal levels.

High-normal TSH values in obesity: is it insulin resistance or adipose tissue's guilt?

OBJECTIVE

Clinical evidences reported subclinical alterations of thyroid function in obesity, although the relationship between thyroid status and obesity remains unclear. We cross-sectionally investigated the influence of metabolic features on hypothalamic-pituitary-thyroid axis in obesity.

DESIGN AND METHODS

We enrolled 60 euthyroid subjects with no history of type 2 diabetes mellitus and assessed the relationship of thyroid function with insulin resistance, measured using euglycemic clamp, and abdominal fat volume, quantified by computed tomography scan (CT scan). Thyroid stimulating hormone (TSH) correlated with BMI (r = 0.46; P = 0.02), both visceral (r = 0.58; P = 0.02) and subcutaneous adipose tissue volumes (r = 0.43; P = 0.03) and insulin resistance (inverse relationship with insulin sensitivity-glucose uptake: r = -0.40; P = 0.04).

RESULTS

After performing multivariate regression, visceral adipose tissue volume was found to be the most powerful predictor of TSH (β = 3.05; P = 0.01), whereas glucose uptake, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, subcutaneous adipose tissue volume, and triglycerides were not. To further confirm the hypothesis that high-normal TSH values could be dependent on adipose tissue, and not on insulin resistance, we restricted our analyses to moderately obese subjects' BMI ranging 30-35 kg/m(2). This subgroup was then divided as insulin resistant and insulin sensitive according to the glucose uptake (≤ or >5 mg · kg(-1) · min(-1), respectively). We did not find any statistical difference in TSH (insulin resistant: 1.62 ± 0.65 µU/ml vs. insulin sensitive: 1.46 ± 0.48; P = not significant) and BMI (insulin resistant: 32.2 ± 1.6 kg/m(2) vs. insulin sensitive: 32.4 ± 1.4; P = not significant), thus confirming absence of correlation between thyroid function and insulin sensitivity per se.

CONCLUSION

Our study suggests that the increase in visceral adipose tissue is the best predictor of TSH concentration in obesity, independently from the eventual concurrent presence of insulin resistance.

Risk Factors for Thyroid Dysfunction among Type 2 Diabetic Patients in a Highly Diabetes Mellitus Prevalent Society

Diabetes and thyroid dysfunction found to exist simultaneously. In this regard, the present study looked into the prevalence of different forms of thyroid dysfunction and their risk factors among Type 2 diabetic Saudi patients. Methodology. A cross-sectional retrospective randomized hospital-based study of 411 Type 2 diabetic Saudi patients of >25 years of age was conducted to test the prevalence of different types of thyroid dysfunction and their risk factors. Results. The prevalence of different types of thyroid dysfunction is 28.5%, of which 25.3% had hypothyroidism, where 15.3%, 9.5%, and 0.5% are clinical, subclinical, and overt hypothyroidism, respectively. The prevalence of hyperthyroidism is 3.2%, of which subclinical cases accounted for 2.7% and overt hyperthyroidism accounted for 0.5%. Risk factors for thyroid dysfunction among Saudi Type 2 diabetic patients are family history of thyroid disease, female gender, and duration of diabetes of >10 years, while the risk was not significant in patients with history of goiter and patients aged >60 years. Smoking and parity show a nonsignificant reduced risk. Conclusion. Thyroid dysfunction is highly prevalent among Saudi Type 2 diabetic patients, and the most significant risk factors are family history of thyroid disease, female gender, and >10 years duration of diabetes.

Hepatic steatosis and thyroid function tests in overweight and obese children

Objectives. Associations between thyroid function and nonalcoholic fatty liver disease (NAFLD) are unknown in childhood. Thus, the aim of the present study was to investigate in 402 consecutive overweight/obese children the association between thyroid function tests and hepatic steatosis as well as metabolic variables. Methods. Hepatic steatosis was diagnosed by ultrasound after exclusion of infectious and metabolic disorders. Fasting serum samples were taken for determination of thyroid function (TSH, FT4, and FT3), along with alanine aminotransferase (ALT), lipid profile, glucose, insulin, and insulin resistance (IR). Results. Eighty-eight children (21.9%) had TSH above the normal range (>4.0 mIU/L). FT3 and FT4 were within the reference intervals in all subjects. Elevated TSH was associated with increased odds of having hepatic steatosis (OR 2.10 (95% CI, 1.22-3.60)), hepatic steatosis with elevated ALT (2.42 (95% CI, 1.29-4.51)), hypertriglyceridemia, elevated total cholesterol, and IR as well as metabolic syndrome (considered as a single clinical entity), after adjustment for age, gender, pubertal status, and body mass index-SD score (or waist circumference). Conclusions. In overweight/obese children, elevated TSH concentration is a significant predictor of hepatic steatosis and lipid and glucose dysmetabolism, independently of the degree of total and visceral obesity.

Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association

BACKGROUND

Hypothyroidism has multiple etiologies and manifestations. Appropriate treatment requires an accurate diagnosis and is influenced by coexisting medical conditions. This paper describes evidence-based clinical guidelines for the clinical management of hypothyroidism in ambulatory patients.

METHODS

The development of these guidelines was commissioned by the American Association of Clinical Endocrinologists (AACE) in association with American Thyroid Association (ATA). AACE and the ATA assembled a task force of expert clinicians who authored this article. The authors examined relevant literature and took an evidence-based medicine approach that incorporated their knowledge and experience to develop a series of specific recommendations and the rationale for these recommendations. The strength of the recommendations and the quality of evidence supporting each was rated according to the approach outlined in the American Association of Clinical Endocrinologists Protocol for Standardized Production of Clinical Guidelines-2010 update.

RESULTS

Topics addressed include the etiology, epidemiology, clinical and laboratory evaluation, management, and consequences of hypothyroidism. Screening, treatment of subclinical hypothyroidism, pregnancy, and areas for future research are also covered.

CONCLUSIONS

Fifty-two evidence-based recommendations and subrecommendations were developed to aid in the care of patients with hypothyroidism and to share what the authors believe is current, rational, and optimal medical practice for the diagnosis and care of hypothyroidism. A serum thyrotropin is the single best screening test for primary thyroid dysfunction for the vast majority of outpatient clinical situations. The standard treatment is replacement with L-thyroxine. The decision to treat subclinical hypothyroidism when the serum thyrotropin is less than 10 mIU/L should be tailored to the individual patient.

Thyroid function tests in metabolic syndrome

OBJECTIVE

We evaluated the thyroid function tests in individuals with metabolic syndrome to explore the possibility of thyroid receptor resistance.

MATERIALS AND METHODS

The study was a cross-sectional study. It included 40 patients (group I) and 20 healthy individuals served as controls (group II). Patients in group I fulfilled the three or more of the NCEP ATP III (National Cholesterol Education Programme - Adult Treatment Panel III) criterion to define the metabolic syndrome. Blood sugar and serum insulin levels were measured in both the groups. All the patients (group I) had insulin resistance as per the HOMA IR (the homeostasis model for insulin resistance) model. The HOMA IR value obtained in group II individuals served as a reference mark to define insulin resistance. T(3), T(4), TSH levels were measured as indicators of thyroid functions. There was an increase in TSH levels with normal T(3) and T(4) in group I indicating that increased TSH probably due to thyroid receptor resistance may be a part of metabolic syndrome rather than a state of hypothyroidism.

RESULTS

T(3) and T(4) levels were comparable in patients and controls. There was a significant increase in TSH levels in patients as compared to the controls.

CONCLUSION

Raised TSH in patients with metabolic syndrome independent of lowered T(3) and T(4) suggest it to be a part and parcel of this syndrome.

Body composition and metabolic parameters are associated with variation in thyroid hormone levels among euthyroid young men

OBJECTIVE

Thyroid disorders affect metabolism and body composition. Existing literature has been conflicting on whether this is also the case for thyroid hormone levels within the euthyroid range. Therefore, we have investigated the relationship between thyroid hormone concentrations and body composition together with metabolic parameters in a population of healthy euthyroid men.

METHODS

Healthy male siblings (n=941, 25-45 years, median BMI 24.6) were recruited in a cross-sectional, population-based study; a history or treatment of thyroid disease and thyroid autoimmunity were exclusion criteria. Body composition and muscle cross-sectional area were assessed by dual-energy X-ray absorptiometry and peripheral quantitative computed tomography. Total (triiodothyronine (T(3); TT(3)) thyroxine and (T(4); TT(4))) and free thyroid hormones (FT(3) and FT(4)), TSH, and reverse T(3) (rT(3)) and thyroid-binding globulin (TBG) were determined using immunoassays.

RESULTS

BMI was positively associated with (F)T(3) (P<0.0001). Whole body fat mass displayed positive associations with TT(3) and with (F)T(4) and TBG (P≤0.0006). Positive associations were further observed between leptin and (F)T(3), TT(4), and TBG (P≤0.0002). Inverse associations between lean mass and muscle cross-sectional area and (F)T(3), (F)T(4), and TBG were observed (P≤0.0003). Higher levels of (F)T(3) and TBG were associated with lower insulin sensitivity, assessed by homeostatic model assessment of insulin resistance (IR; P≤0.0001). No associations between TSH and body composition or metabolic parameters were seen.

CONCLUSION

We show that a less favorable body composition (with higher fat and lower muscle mass and accompanying higher leptin concentrations) and IR are associated with higher thyroid hormone levels in healthy young men with well characterized euthyroidism.

Thyroid hormone and obesity

PURPOSE OF REVIEW

To review several of the most recent and most important clinical studies regarding the effects of thyroid treatments on weight change, associations between thyroid status and weight, and the effects of obesity and weight change on thyroid function.

RECENT FINDINGS

Weight decreases following treatment for hypothyroidism. However, following levothyroxine treatment for overt hypothyroidism, weight loss appears to be modest and mediated primarily by loss of water weight rather than fat. There is conflicting evidence about the effects of thyroidectomy on weight. In large population studies, even among euthyroid individuals, serum thyroid-stimulating hormone is typically positively associated with body weight and BMI. Both serum thyroid-stimulating hormone and T3 are typically increased in obese compared with lean individuals, an effect likely mediated, at least in part, by leptin. Finally, there is no consistent evidence that thyroid hormone treatment induces weight loss in obese euthyroid individuals, but thyroid hormone analogues may eventually be useful for weight loss.

SUMMARY

The interrelationships between body weight and thyroid status are complex.

A myriad of pathways to NASH

Nonalcoholic steatohepatitis (NASH) is defined histopathologically by the presence of macrovesicular steatosis, cellular ballooning, and inflammation. NASH represents a complex multifactorial disease that typically occurs within the context of the metabolic syndrome. NASH lacks homogeneity, and other forms of NASH can present atypically. Less than 50% of patients with NASH respond to pharmacologic treatment, which speaks to this heterogeneity. The authors discuss drugs, disease entities, and nutritional states that can cause or exacerbate underlying NASH indirectly through worsening insulin resistance or directly by interfering with lipid metabolism, promoting oxidative injury, or activating inflammatory pathways.

Prevalence of endocrine disorders in morbidly obese patients and the effects of bariatric surgery on endocrine and metabolic parameters

BACKGROUND

Several endocrine abnormalities, including hypothyroidism and Cushing's syndrome (CS), are considered as causative factors of obesity. The aim of this study was to evaluate the prevalence of endocrine disorders and obesity-associated co-morbidities, as well as the impact of substantial weight loss.

METHODS

Screening was performed in 433 consecutive morbidly obese patients (age 41 ± 12 years; BMI 47 ± 6.9 kg/m(2); women 76%). A 1-mg dexamethasone suppression test (1-mg DST) was conducted to exclude CS, and thyrotropin (TSH) was measured to exclude hypothyroidism. Insulin sensitivity was estimated from oral glucose tolerance tests employing the Clamp-like index. Examinations were carried out at baseline, as well as at 6 and 12 months postoperatively.

RESULTS

The prevalence of CS was below 0.6%. Before surgery, TSH was elevated compared to an age- and sex-matched normal weight control group (2.4 ± 1.2 vs. 1.5 ± 0.7 μU/ml; p < 0.001). The NCEP criteria of metabolic syndrome (MetS) were fulfilled by 39.5% of the patients. Impaired glucose tolerance and diabetes mellitus were observed in 23.5% and 22.6%, respectively. Seventy-two percent were insulin resistant. During follow-up, weight (BMI 47 ± 6.9 vs. 36 ± 6.4 vs. 32 ± 6.6 kg/m(2); p < 0.001) and TSH decreased significantly (2.4 ± 1.2 vs. 1.8 ± 1.0 vs. 1.8 ± 1.0 μU/ml; p < 0.001). Serum cortisol was higher in the MetS(+)-group compared to the MetS(-)-group (15.0 ± 6.3 vs. 13.5 ± 6.3 μg/dl; p = 0.003).

CONCLUSIONS

CS appears to be a rare cause of morbid obesity. Normalization of slightly elevated thyrotropin after weight loss suggests that obesity causes TSH elevation rather than the reverse.

Morbid obesity in women is associated to a lower prevalence of thyroid nodules

BACKGROUND

Few studies have recently showed functional and morphological changes of the thyroid gland in relation to obesity. To our knowledge, no data are available about the prevalence of thyroid nodules in female obese patients. The aim of this study was to investigate the prevalence of thyroid nodules in morbidly obese women.

METHODS

One hundred eight consecutive female obese patients were selected from those referred to our medical and surgery outpatients providing that following criteria were satisfied: (1) affected by morbid obesity (body mass index (BMI) >40 kg/m(2)); (2) no previous diagnosis of thyroid disease; (3) biochemically proven euthyroid state at the time of recruitment. Ninety-seven control subjects, constituted by normo-weight and/or slightly overweight (BMI ≤ 30 kg/m(2)) women, should satisfy the above criteria 2 and 3. All the subjects were submitted to ultrasound investigation.

RESULTS

The two groups of patients displayed no differences for age and fT4 levels. Obese patients clearly showed a lower prevalence of thyroid nodules [odds ratio 0.294, 95% confidence interval 0.206-0.382]. A single nodule was found in 23% of obese patients as compared to 65% of control subjects (p < 0.0001). No difference for age (year) was found between obese and non-obese subjects with nodules (40.5 ± 8.2 vs. 44.2 ± 8.9, respectively, p = 0.07).

CONCLUSIONS

Our data clearly show a significantly lower prevalence of thyroid nodules in morbidly obese patients. Further studies are needed to confirm and to understand this first observation.

Prevalence of hypothyroidism in nonalcoholic fatty liver disease

BACKGROUND

A possible association between nonalcoholic fatty liver disease (NAFLD) and hypothyroidism has been suggested. The recognized link between hypothyroidism and elements of the metabolic syndrome may explain this association.

AIM

The purpose of this study was to determine the prevalence of hypothyroidism in a cohort of patients with NAFLD and analyze the potential factors associated with hypothyroidism in this patient population.

METHODS

Two hundred forty-six patients with biopsy-proven NAFLD attending hepatology clinics at the Cleveland Clinic between October 2006 and June 2009, and 430 age-, gender-, race- and BMI-matched control subjects seen in the general internal medicine clinic were included. Patients with a clinical diagnosis of hypothyroidism who were on thyroid replacement therapy were considered to be hypothyroid.

RESULTS

Hypothyroidism was more frequent among patients with NAFLD (21% vs. 9.5%; P < 0.01) compared to controls, and was higher in NASH patients than NAFLD patients without NASH (25% vs. 12.8%, P = 0.03). Subjects with hypothyroidism were 2.1 (95% CI 1.1-3.9, P = 0.02) and 3.8 (95% CI 2-6.9, P < 0.001) times more likely to have NAFLD and NASH, respectively. By multivariate analysis, female gender (P < 0.001) and increased BMI (P = 0.03) were associated with hypothyroidism. NAFLD subjects who reported mild alcohol consumption were less likely to have hypothyroidism compared to those who reported complete abstinence (OR 0.37, P = 0.008).

CONCLUSIONS

A higher prevalence of hypothyroidism was demonstrated in patients with NAFLD compared to controls. Among subjects with NALFD, female gender, increased BMI and history of abstinence from alcohol were associated with hypothyroidism. Patients with hypothyroidism were also more likely to have NASH.

Effect of weight loss after gastric bypass surgery on thyroid function in euthyroid people with morbid obesity

Obesity is positively associated with serum thyrotropin (TSH) concentrations at the high end of the normal range. The relationship between weight loss and thyroid function is less clear and studies to date have yielded inconsistent results. Our aim was to describe changes in thyroid function in obese people in relation to durable and significant weight loss after Roux-en-Y gastric bypass (RYGB) surgery. We recorded percentage of excess weight loss (% EWL), serum TSH and free thyroxine (fT4) before and median 4.5, 15 and 24 months after RYGB in 55 euthyroid patients with morbid obesity ranging in age from 18 to 64 years in a retrospective cohort analysis in a university hospital in Greater Manchester. Mean ± standard error preoperative weight was 135.13 ± 4.23 kg and BMI 48.08 ± 1.58 kg m(-2) . Patients attained nadir %EWL of 68% by median 15 months after RYGB. TSH was 2.00 ± 0.14 mU L(-1) at baseline and 2.02 ± 0.22 mU L(-1) at 24 months after RYGB (non-significant). Baseline fT4 was 13.46 ± 0.28 pmol L(-1) , and increased significantly to 15.14 ± 0.55 pmol L(-1) at 24 months (P < 0.004). In conclusion, we report that weight loss after RYGB was accompanied by significant increase in serum fT4 but no change in TSH concentrations. Further study to elucidate the effect of significant weight loss on the thyroid axis is required.

Association of metabolic syndrome parameters with TT3 and FT3/FT4 ratio in obese Turkish population

BACKGROUND

Obesity and metabolic syndrome are major health problems worldwide, including Turkey. Recent studies have shown an association between thyroid function tests and metabolic syndrome parameters. In this study, we aimed to determine the frequency of metabolic syndrome in an obese Turkish population and the relationship between metabolic syndrome and thyroid functions.

MATERIALS AND METHOD

We recruited 211 patients (187 females/24 males; mean age, 39.7±11.7 years) with body mass index (BMI) >30 kg/m(2) and no other hormonal pathology that could cause obesity. Anthropometric evaluation was followed by measurement of fasting blood glucose (FBG), insulin, total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), thyroid-stimulating hormone (TSH), total triiodothyronine (TT3), total thyroxine (TT4), free T3 (FT3), and free T4 (FT4). Metabolic syndrome was defined according to the 2005 revision of the National Cholesterol Education Program Adult Panel III (NCEP ATP III) criteria. Insulin resistance was calculated from homeostasis model assessment of insulin resistance (HOMA-IR) formula. The TSH cutoff value was set at 2.5 mU/L.

RESULTS

Metabolic syndrome was diagnosed in 122 patients (58%). Metabolic syndrome positive patients had significantly higher FBG, triglycerides, FT4, systolic (SBP) and diastolic blood pressure (DBP), and statistically lower HDL-C and FT3/FT4 ratio than metabolic syndrome negative patients. TSH decreased with age and was not related with any metabolic syndrome parameters. The FT3/FT4 ratio negatively correlated with FBG, triglycerides, SBP, and DBP (P=0.003, r=-38; P=0.02, r=-0.28; P=0.005, r=-0.35; and P=0.007, r=-0.34, respectively); TT3 positively correlated with HOMA-IR (P=0.006, r=0.40), FBG (P=0.009, r=0.38), and waist circumference (P=0.02, r=0.34).

CONCLUSION

Metabolic syndrome frequency was increased in our study population compared to the general population. Metabolic syndrome parameters (except HDL) correlated with TT3, FT4, and the FT3/FT4 ratio. FT4 levels were associated with obesity and metabolic syndrome independently of insulin resistance, whereas TT3 levels were associated with both insulin resistance and metabolic syndrome. This relationship can be explained by compensatory effects of TT3, and probably FT4, on energy expenditure and thermogenesis in obese people.