Subclinical hypothyroidism and its relation to obesity in patients before and after Roux-en-Y gastric bypass

Treatment of Obesity with Thyroid hormones in Europe. Data from the THESIS* Collaboration

PURPOSE

The use of thyroid hormones (TH) to treat obesity is unsupported by evidence as reflected in international guidelines. We explored views about this practice, and associations with respondent characteristics among European thyroid specialists.

METHODS

Specialists from 28 countries were invited to a survey via professional organisations. The relevant question was whether "Thyroid hormones may be indicated in biochemically euthyroid patients with obesity resistant to lifestyle interventions".

RESULTS

Of 17,232 invitations 5695 responses were received (33% valid response rate; 65% women; 90% endocrinologists). Of these, 290 (5.1%) stated that TH may be indicated as treatment for obesity in euthyroid patients. This view was commoner among non-endocrinologists (8.7% vs. 4.7%, p < 0.01), private practice (6.5% vs. 4.5%, p < 0.01), and varied geographically (Eastern Europe, 7.3%; Southern Europe, 4.8%; Western Europe, 2.7%; and Northern Europe, 2.5%). Respondents from Northern and Western Europe were less likely to use TH than those from Eastern Europe (p < 0.01). Gross national income (GNI) correlated inversely with this view (OR 0.97, CI: 0.96-0.97; p < 0.001). Having national guidelines on hypothyroidism correlated negatively with treating obesity with TH (OR 0.71, CI: 0.55-0.91).

CONCLUSIONS

Despite the lack of evidence, and contrary to guidelines' recommendations, about 5% of respondents stated that TH may be indicated as a treatment for obesity in euthyroid patients resistant to life-style interventions. This opinion was associated with (i) respondent characteristics: being non-endocrinologist, working in private practice, treating a small number of hypothyroid patients annually and (ii) national characteristics: prevalence of obesity, Eastern Europe, low GNI and lack of national hypothyroidism guidelines.

Relationship between sleep abnormalities and hypothyroidism: results from the National Health and Nutrition Examination Survey 2007-2012

BACKGROUND

Studies have emphasised the adverse effects of poor sleep on human health, however, the correlation between sleep abnormalities and hypothyroidism remains unclear. This study evaluated whether sleep abnormalities may be related to increased prevalence of hypothyroidism in general US adults.

METHODS

In total, 9016 adults who participated in the National Health and Nutrition Examination Survey from 2007 to 2012 were analysed. A standardised questionnaire was used to collect data regarding sleep duration, self-reported trouble sleeping and sleep disorders. Values were assigned to the three aforementioned sleep factors, resulting in an overall sleep score of 0-3. The sleep patterns were divided into healthy sleep pattern (overall sleep score = 3), intermediate sleep pattern (overall sleep score = 2) and poor sleep pattern (overall sleep score = 0 or 1) according to a former study. Hypothyroidism was defined as thyroid-stimulating hormone (TSH) levels > 5.6 mIU/mL or the need to take thyroid hormones. Multivariable logistic regression analysis was performed to assess the relationship between sleep abnormalities and hypothyroidism.

RESULTS

The overall prevalence of hypothyroidism was 8.0% among the 9016 participants. Self-reported trouble sleeping (odds ratio [OR] = 1.38, 95% CI: 1.14-1.68, p = 0.001) and sleep disorders (OR = 1.40, 95% CI: 1.06-1.86, p = 0.0196) were associated with increased prevalence of hypothyroidism. Neither short sleep duration (OR = 0.99, 95% CI: 0.82-1.19) nor long sleep duration (OR = 0.98, 95% CI: 0.61-1.58) was significantly associated with hypothyroidism. Moreover, poor sleep pattern was significantly associated with increased prevalence of hypothyroidism (OR = 1.30, 95% CI: 1.03-1.66, p = 0.0301).

CONCLUSIONS

Both trouble sleeping and sleep disorders were associated with increased prevalence of hypothyroidism.

Thyroid-stimulating hormone levels in euthyroid patients 8 years following bariatric surgery

Background

Bariatric surgery (BS) was shown to promote a decline in thyroid-stimulating hormone (TSH) in euthyroid patients with severe obesity in the short-term. Aim of the present study was to assess the effect of weight loss on thyroid function in euthyroid patients in the long-term following different bariatric procedures.

Methods

In a retrospective cohort study including 135 patients at baseline, thyroid function was assessed at six time points up to 8 years after surgery. Patients were stratified by TSH levels at baseline and divided into two groups to compare the change in TSH at long-time. We used log-linear regression to assess the relation between thyroid hormones and TSH and linear regression analyses to identify variables that were thought to determine TSH and fT3/fT4-ratio as well as their change long-term.

Results

Over a mean follow-up of 8 years, TSH and fT3/fT4-ratio declined (both p < 0.001). Patients with high-normal TSH showed a greater decline in TSH than those with normal TSH compared to baseline. Thyroid hormones and TSH displayed a negative log-linear correlation at long-term follow-up. Change in TSH at long-time showed a negative correlation with TSH at baseline (B = −0.55; p < 0.001). With regard to type of surgery, there were no significant differences in TSH.

Conclusion

BS promotes a decline of TSH in euthyroid patients up to 8 years after intervention despite weight regain. The greatest change in TSH was seen among patients with high-normal baseline-TSH. Results of log-linear regression suggest recovery of the pituitary-thyroid axis. Type of surgery did not affect the change in TSH levels over time.

Laparoscopic Sleeve Gastrectomy has A Positive Impact on Subclinical Hypothyroidism Among Obese Patients: A Prospective Study

BACKGROUND

The effect of bariatric surgery on postoperative thyroid function remains incompletely understood. In this study, we aimed to evaluate the changes in thyroid functions after gastric sleeve operation for morbidly obese Egyptian patients.

METHODS

This was a prospective study that recruited 128 patients who underwent sleeve gastrectomy through the period from December 2016 to April 2020. We measured thyroid-stimulating hormone (TSH), free thyroxin (FT4), and free triiodothyronine. Subclinical hypothyroidism was defined by a TSH level > 4.5 mIU/L but a normal FT4 level. All patients were followed for 12 months after the procedure.

RESULTS

Preoperatively, 30 (23.4%) patients had subclinical hypothyroidism. The prevalence of subclinical hypothyroidism decreased significantly to reach 7.8% at the end of follow-up (p < 0.001). None of the patients developed de novo hypothyroidism at the end of follow-up. Patients with subclinical hypothyroidism were more likely to be females (p = 0.037) and had significantly higher waist circumference (p < 0.001), DBP (p = 0.02), serum cholesterol (p < 0.001), and serum triglyceride (p < 0.001). However, patients with subclinical hypothyroidism at the end of follow-up had significantly higher BMI at the end of the sixth month (p = 0.048). Similarly, patients with subclinical hypothyroidism at the end of follow-up had significantly higher serum cholesterol (p = 0.002), LDL, (p = 0.038), and serum triglyceride (p < 0.001) at the end of the sixth months of follow-up. A similar trend was noted at the end of the 12th month. The preoperative value of serum TSH correlated significantly with serum cholesterol and triglyceride levels.

CONCLUSION

The positive effect of the LSG procedure on the hypothyroid bariatric population, including enhanced thyroid function, was demonstrated.

Metabolic and Psychological Features are Associated with Weight Loss 12 Months After Sleeve Gastrectomy

CONTEXT

Laparoscopic sleeve gastrectomy (LSG) is a recognized effective procedure of bariatric surgery, but a poor response in weight loss may still represent a clinical problem. To date there are no validated predictors useful to better perform patient selection.

OBJECTIVE

To establish the association of baseline anthropometric, metabolic, and psychologic features with the percent total weight loss (%TWL) and percent excess weight loss (%EWL) 12 months after surgery.

DESIGN

Retrospective longitudinal analysis of a set of data about obese patients attending the outpatient service of a single obesity center from June 2016 to June 2019.

PATIENTS

A total of 106 obese patients underwent LSG with presurgery evaluation and follow-up at 12 months after surgery.

MAIN OUTCOME

Weight loss 12 months after LSG.

RESULTS

Patients who achieved a %TWL higher than the observed median (≥34%) were younger, with a lower fasting plasma glucose and glycated hemoglobin, with a lower prevalence of hypertension and with a lower score in the impulsiveness scale, compared with patients with a %TWL < 34%. Similar findings were found when %EWL was considered. Multivariable stepwise regression analysis showed that younger age, lower impulsiveness, higher-than-normal urinary free cortisol, and lower HbA1c were associated with higher %TWL, explaining about 31.5% of the weight loss.

CONCLUSION

Metabolic and psychologic features at baseline were independently associated with weight loss and explained a non-negligible effect on the response to LSG. These data suggest that careful metabolic and psychologic profiling could help in sharper indications and personalized pre- and postsurgical follow-up protocols in candidates for LSG.

The Effect of Laparoscopic Sleeve Gastrectomy on Serum Thyroid-Stimulating Hormone Levels in Obese Patients with Overt and Subclinical Hypothyroidism: a 7-Year Retrospective Study

BACKGROUND

Inconsistent results were reported by several studies that evaluated the effect of weight loss induced by bariatric surgery on thyroid function panel. This study is aimed at evaluating this effect on thyroid-stimulating hormone (TSH) and thyroid hormone replacement dosages in obese population with overt and subclinical hypothyroidism (SH).

METHODS

A retrospective study was performed on all morbidly obese patients with previous diagnosis of overt and subclinical hypothyroidism who underwent laparoscopic sleeve gastrectomy from October 2009 to January 2017. The correlation between TSH and body mass index (BMI) and the effect of weight loss induced by bariatric surgery on TSH were investigated.

RESULTS

The prevalence of overt and SH in morbidly obese patients was 10.8% and 7.2%, respectively. Thirty-six hypothyroid patients and 67 subclinically hypothyroid patients were included in the study. Hypothyroidism improved in 44.5% of patients and completely resolved in 22.2%, and 33.3% experienced no change. Ninety-one percent of SH patients completely resolved, 6% improved, but 3% worsened, with one patient developed hypothyroidism. Both groups achieved a significant decrease in postoperative BMI. A positively statistically significant association was found between BMI and TSH (p < 0.005).

CONCLUSIONS

Our results favor the effect of laparoscopic sleeve gastrectomy in the obese population with overt and SH as shown by the majority of SH resolution and overt hypothyroidism improvement.

Thyroid-stimulating hormone and free thyroxine fail to predict the severity and clinical course of hyperemesis gravidarum: A prospective cohort study

Introduction

Little is known about the pathophysiology of hyperemesis gravidarum (HG). Proposed underlying causes are multifactorial and thyroid function is hypothesized to be causally involved. In this study, we aimed to assess the utility of thyroid‐stimulating hormone (TSH) and free thyroxine (FT4) as a marker and predictor for the severity and clinical course of HG.

Material and methods

We conducted a prospective cohort study including women admitted for HG between 5 and 20 weeks of gestation in 19 hospitals in the Netherlands. Women with a medical history of thyroid disease were excluded. TSH and FT4 were measured at study entry. To adjust for gestational age, we calculated TSH multiples of the median (MoM). We assessed HG severity at study entry as severity of nausea and vomiting (by the Pregnancy Unique Quantification of Emesis and nausea score), weight change compared with prepregnancy weight, and quality of life. We assessed the clinical course of HG as severity of nausea and vomiting and quality of life 1 week after inclusion, duration of hospital admissions, and readmissions. We performed multivariable regression analysis with absolute TSH, TSH MoMs, and FT4.

Results

Between 2013 and 2016, 215 women participated in the cohort. TSH, TSH MoM, and FT4 were available for, respectively, 150, 126, and 106 of these women. Multivariable linear regression analysis showed that lower TSH MoM was significantly associated with increased weight loss or lower weight gain at study entry (ΔKg; β = 2.00, 95% CI 0.47‐3.53), whereas absolute TSH and FT4 were not. Lower TSH, not lower TSH MoM or FT4, was significantly associated with lower nausea and vomiting scores 1 week after inclusion (β = 1.74, 95% CI 0.36‐3.11). TSH and FT4 showed no association with any of the other markers of the severity or clinical course of HG. Twenty‐one out of 215 (9.8%) women had gestational transient thyrotoxicosis. Women with gestational transient thyrotoxicosis had a lower quality of life 1 week after inclusion than women with no gestational transient thyrotoxicosis (p = 0.03).

Conclusions

Our findings show an inconsistent role for TSH, TSH MoM, or FT4 at time of admission and provide little guidance on the severity and clinical course of HG.

Hypothyroidism and levothyroxine therapy following bariatric surgery: a systematic review, meta-analysis, network meta-analysis, and meta-regression

BACKGROUND

Many health benefits of bariatric surgery are known and well-studied, but there is scarce data on the benefits of bariatric surgery on the thyroid function.

OBJECTIVE

We aimed to make a meta-analysis regarding the impact of bariatric surgery on thyroid-stimulating hormone (TSH) levels, levothyroxine dose, and the status of subclinical hypothyroidism.

SETTING

Systematic review and meta-analysis.

METHODS

PubMed, EMBASE, and Cochrane Library were searched up to December 2020 for relevant clinical studies. Random-effects model was used to pool results. Network meta-analysis was performed, incorporating direct and indirect comparisons among different types of bariatric surgery. Meta-regression analysis was performed to evaluate the impact of moderator variables on TSH levels and required levothyroxine dose after surgery. We followed the PRISMA guidelines for data selection and extraction. PROSPERO registry number: CRD42018105739.

RESULTS

A total of 28 studies involving 1284 patients were included. There was a statistically significant decrease in TSH levels after bariatric surgery (mean difference = -1.66 mU/L, 95%CI [-2.29, -1.03], P < .0001). In meta-regression analysis, we found that the following moderator variables: length of follow-up, mean age, baseline TSH, and preoperative thyroid function, could explain 1%, 43%, 68%, and 88% of the between-study variance, respectively. Furthermore, subclinical hypothyroidism was completely resolved in 87% of patients following bariatric surgery. In addition, there was a statistically significant decrease of levothyroxine dose in frank hypothyroid patients following bariatric surgery (mean difference = -13.20 mcg/d, 95%CI [-19.69, -6.71]). In network meta-analysis, we found that discontinuing or decreasing levothyroxine dose was significant following Roux-en-Y gastric bypass, 1 anastomosis gastric bypass, and sleeve gastrectomy, (OR = 31.02, 95%CI [10.34, 93.08]), (OR = 41.73, 95%CI [2.04, 854.69]), (OR = 104.03, 95%CI [35.79, 302.38]), respectively.

CONCLUSIONS

Based on our meta-analysis, bariatric surgery is associated with the resolution of subclinical hypothyroidism, a decrease in TSH levels, and a decrease in levothyroxine dose.

Long Work Hours Are Associated with Hypothyroidism: A Cross-Sectional Study with Population-Representative Data

Background: Studies have highlighted the adverse effects of long work hours on workers' health; however, the association of long work hours with thyroid function has not been studied. This study aimed at assessing long work hours as a risk factor for thyroid dysfunction. Methods: This cross-sectional study was based on data obtained from the Korea National Health and Nutrition Examination Survey conducted from 2013 to 2015. A total of 2160 adults who worked 36-83 hours per week were included. Thyroid function was defined based on the population thyroid-stimulating hormone reference ranges, after excluding individuals with positive results for thyroid peroxidase antibody. The association between work hours and thyroid function was confirmed via multinomial logistic regression. Results: Hypothyroidism was more prevalent among those with longer work hours (3.5% vs. 1.4% for 53-83 and 36-42 work hours per week, respectively). Individuals who worked longer hours had an increased odds for hypothyroidism (odds ratio 1.46, confidence interval 1.12 - 1.90, per 10-hour increase in work hours per week), after adjustment for age, sex, body mass index, urine iodine concentration, smoking status, work schedule, and socioeconomic status. The association between work hours and hypothyroidism was consistent in various subgroups stratified by sex or socioeconomic status. Conclusions: To our knowledge, this study is the first to show that long work hours are associated with hypothyroidism. Further large longitudinal studies are needed to clarify causality.

Thyroid Hormone Changes After Sleeve Gastrectomy With and Without Antral Preservation

BACKGROUND

The effect of bariatric surgery on thyroid hormone changes yielded inconsistent results. The aim of the present study was to assess the change of thyroid hormone levels following laparoscopic sleeve gastrectomy (LSG), with or without antral preservation (AP).

METHODS

Thyroid hormones (TSH, FT3, FT4) were examined preoperatively, at the end of the first postoperative month, and first postoperative year. Secondly, antral resection (AR) and AP were compared at inducing weight loss and thereby affecting thyroid hormone levels.

RESULTS

Euthyroid obese patients (86 female/20 male) underwent LSG. Of these, 58 patients underwent AR and 48 patients AP. The mean FT3 levels significantly decreased both in the first postoperative month and the first year (P < 0.001), whereas mean TSH levels decreased significantly in the first postoperative year (P < 0.001). FT4 levels remained nearly unchanged (P = 0.517). Postoperative first year body mass index (BMI) loss, excess BMI loss percentile (%EBMIL), and total body weight loss percentile (%TWL) were significantly higher in AR group than the AP group (P ≤ 0.01). When the change in thyroid hormone levels was analyzed by pyloric distance according to time periods, no significant difference was found in TSH and FT4 levels (P > 0.05); however, reduction in FT3 levels was significantly greater in patients with AR than in AP patients (P = 0.028).

CONCLUSION

LSG promotes significant reduction in TSH and FT3 levels, whereas FT4 levels remain unchanged. LSG with AR provides more weight loss in short term and appears to be more effective at lowering FT3 levels.

Thyroid-Gut-Axis: How Does the Microbiota Influence Thyroid Function?

A healthy gut microbiota not only has beneficial effects on the activity of the immune system, but also on thyroid function. Thyroid and intestinal diseases prevalently coexist-Hashimoto's thyroiditis (HT) and Graves' disease (GD) are the most common autoimmune thyroid diseases (AITD) and often co-occur with Celiac Disease (CD) and Non-celiac wheat sensitivity (NCWS). This can be explained by the damaged intestinal barrier and the following increase of intestinal permeability, allowing antigens to pass more easily and activate the immune system or cross-react with extraintestinal tissues, respectively. Dysbiosis has not only been found in AITDs, but has also been reported in thyroid carcinoma, in which an increased number of carcinogenic and inflammatory bacterial strains were observed. Additionally, the composition of the gut microbiota has an influence on the availability of essential micronutrients for the thyroid gland. Iodine, iron, and copper are crucial for thyroid hormone synthesis, selenium and zinc are needed for converting T4 to T3, and vitamin D assists in regulating the immune response. Those micronutrients are often found to be deficient in AITDs, resulting in malfunctioning of the thyroid. Bariatric surgery can lead to an inadequate absorption of these nutrients and further implicates changes in thyroid stimulating hormone (TSH) and T3 levels. Supplementation of probiotics showed beneficial effects on thyroid hormones and thyroid function in general. A literature research was performed to examine the interplay between gut microbiota and thyroid disorders that should be considered when treating patients suffering from thyroid diseases. Multifactorial therapeutic and preventive management strategies could be established and more specifically adjusted to patients, depending on their gut bacteria composition. Future well-powered human studies are warranted to evaluate the impact of alterations in gut microbiota on thyroid function and diseases.

Interaction effect of obesity and thyroid autoimmunity on the prevalence of hyperthyrotropinaemia

PURPOSE

The role of thyroid autoimmunity in the association between obesity and hyperthyrotropinaemia remains unclear. We aimed to assess the relationship between obesity, autoimmunity, and hyperthyrotropinaemia.

METHODS

In this population-based cross-sectional study, 12531 Chinese individuals (18-80 years) with thyroid function test were categorized into three groups by body mass index (BMI) and were categorized into three layers by thyroid autoantibodies. Multivariate logistic regression was employed to assess the correlation and interaction effect.

RESULTS

There was no significant difference in prevalence of hyperthyrotropinaemia (P = 0.637) among three BMI groups. After stratification, the difference of serum thyrotropin (P < 0.01) and prevalence of hyperthyrotropinaemia (P < 0.01) between the three groups have significant linear trends at the positive levels of thyroid peroxidase antibody (TPOAb) or/and thyroglobulin antibody (TgAb). When TPOAb and TgAb were positive, the risk of hyperthyrotropinaemia increased 1.857-fold in overweight group and 2.201-fold in obese group compared with normal group. Compared with negative TPOAb and TgAb, the risk of hyperthyrotropinaemia for individuals with two positive antibodies increased 3.310-fold, 4.969-fold, and 5.122-fold in the three BMI groups. The adjusted OR (95% CI) for interaction were 1.033 (0.752-1.419) for overweight and one positive antibodies, 1.935 (1.252-2.990) for overweight and two positive antibodies, 1.435 (0.978-2.105) for obesity and one positive antibodies and 2.191 (1.252-3.832) for obesity and two positive antibodies.

CONCLUSION

Overweight and obesity were associated with hyperthyrotropinaemia only in presence of thyroid autoimmunity, and obesity might aggravate the pathogenic effect of autoimmunity on hyperthyrotropinaemia. There was an interaction effect between obesity and autoimmunity on the prevalence of hyperthyrotropinaemia.

Differences in Calcium Metabolism and Thyroid Physiology After Sleeve Gastrectomy and Roux-En-Y Gastric Bypass

INTRODUCTION

Bariatric surgery may modulate the hormones and elements which maintain thyroid and calcium homeostasis. These adaptations in hormonal and elemental aspects have previously been determined via some studies with variations in their findings. Thyroid volume and 24-h urinary calcium are two parameters which have not been investigated regarding whether they change during the bariatric postsurgical period. This study planned to examine the changes in calcium metabolism and thyroid gland functioning after sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB).

MATERIALS AND METHODS

Seventy-three morbidly obese patients with planned bariatric surgery were enrolled in the study. Before and 12 months after the operation, parathormone (PTH), 25-OH-vitamin D3(25vitD3), TSH, free triiodothyronine (fT3), free thyroxine (fT4), calcium (Ca), 24-h urinary Ca and ultrasonography-guided thyroid volume were measured.

RESULTS

In the beginning, 73 patients were examined and 12 months after surgery out of 25 patients continuing follow-up, 20 (80%) had undergone sleeve gastrectomy (SG) while five (20%) had undergone Roux-en-Y gastric bypass (RYGB). Accompanied by significant BMI decrease, 24-h urinary Ca and thyroid volume did not significantly increase in RYGB, SG, and the whole group after 12 months. The SG group showed a significant drop in TSH (p 0.03) level, while the RYGB group showed significant decreases in fT4 (p 0.00) and fT3 (p 0.00); and significant fT3 decrease (p 0.01) was recorded for the whole group.

CONCLUSION

Bariatric surgery may modify Ca homeostasis and thyroid gland functional status. We documented that these were not statistically significant increases in 24-h urinary Ca level and thyroid volume after 1 year. Further studies are needed to understand the issue, enrolling more patients who underwent the same bariatric procedure and after accounting for the inhibition of supplementary vitamin and mineral effects.

Thyroid function before and after Roux-en-Y gastric bypass: an observational study

BACKGROUND

Population studies have shown a positive association between thyroid-stimulating hormone (TSH) and body mass index. Recent studies have shown a significant increase in the prevalence of subclinical hypothyroidism (SCH) in obesity. Weight reduction after Roux-en-Y gastric bypass (RYGB) seems to significantly decrease TSH levels.

OBJECTIVES

The purpose of this study was to evaluate the prevalence of SCH in obese patients (class II and III) and to observe the behavior of thyroid hormones (TSH, hormone triiodothyronine, thyroxine, free thyroxine) with significant weight loss after RYGB.

SETTING

Hospital Nossa Senhora das Graças, Curitiba, Paraná, Brazil.

METHODS

We retrospectively reviewed the medical records of 215 obese patients who underwent RYGB between 2005 and 2012 with a follow-up of at least 2 years. The study was observational and descriptive. The selected times for clinical and laboratory evaluations were preoperative, 3, 6, 12, and 24 months after the procedure. Association, correlation, and variance analyses were performed.

RESULTS

The prevalence of SCH preoperatively was 9.3%. SCH was corrected in 89.5% of patients 12 months after RYGB. We did not find an association between TSH and BMI (r = .002, P = .971). There was a positive impact of bariatric surgery on all metabolic variables. We showed that serum TSH level had no positive correlation with the presence or absence of metabolic syndrome.

CONCLUSIONS

Weight loss after bariatric surgery leads to normalization of TSH levels in most patients and none developed overt hypothyroidism. Obese patients with SCH should not be treated with thyroid hormone replacement. Serial monitoring of thyroid function after obesity therapy seems to be a reasonable approach.

Sex Differences in the Associations of Obesity With Hypothyroidism and Thyroid Autoimmunity Among Chinese Adults

There is an intensive link between obesity and thyroid dysfunction, but this relationship in Asians is still unclear. This study was conducted to define the impact of obesity on risk of hypothyroidism and thyroid autoimmunity among Chinese adults. A population-based, cross-sectional study was carried out, which enrolled a total of 2,808 Chinese adults. To assess the associations of obesity with hypothyroidism and thyroid autoimmunity, odds ratio (ORs) with 95% confidence intervals (95%CIs) were calculated through logistic regression model, and the correlations of body mass index (BMI) with TPOAb and TGAb were also analyzed. Obese females had higher risk of hypothyroidism (22.7 vs. 15.0%; OR = 1.66, 95%CI 1.10–2.53; P = 0.02) and higher risk of subclinical hypothyroidism (22.1 vs. 13.4%; OR = 1.83, 95%CI 1.20–2.80; P = 0.005) than non-obese females. Multivariate logistic regression analysis found significant associations of obesity with hypothyroidism (Adjusted OR = 1.54, 95%CI 1.00–2.38; P = 0.05) and subclinical hypothyroidism (Adjusted OR = 1.69, 95%CI 1.09–2.63; P = 0.02) in females after adjustment for confounding factors. No association between obesity and hypothyroidism was observed in male participants. Spearman's correlation analysis suggested BMI was significantly and positively correlated with TPOAb (Spearman's r = 0.062, P = 0.022) in men but not in women. Linear regression analysis suggested an obviously positive correlation of BMI with TPOAb in men (β = 0.018, P = 0.015) and an obviously negative correlation of BMI with TGAb in women (β = −0.025, P = 0.012), respectively. The study suggests sex differences in the associations of obesity with hypothyroidism and thyroid autoimmunity among Chinese adults. Further studies are needed to better understand the exact mechanism of sex difference in the obesity-thyroid relationship.

Subclinical hypothyroidism is not a risk factor for polycystic ovary syndrome in obese women of reproductive age

Obese women are at high risk for polycystic ovary syndrome (PCOS). Subclinical hypothyroidism (SCH) has been associated with weight gain, insulin resistance and impaired fertility, which are also factors involved in PCOS. However, there is limited information regarding the influence of SCH on the presence of PCOS. In order to determine whether SCH increases the prevalence of PCOS, we performed a cross-sectional study in a cohort of reproductive-aged obese women. All subjects underwent anthropometric evaluation, laboratory tests and ultrasound examination. Diagnosis of PCOS was based on the Rotterdam criteria. A total of 534 obese women were included and 108 (20.2%) of them were diagnosed with SCH. Patients with SCH showed similar insulin resistance, comparable androgen levels, and higher triglycerides levels (1.7 vs. 1.5 mmol/L, p = .002) compared to those with normal thyroid status. The frequency of PCOS did not differ between the two groups (56.1% for normal thyroid function vs. 60.2% for subclinical hypothyroidism, p = .514). In logistic regression analysis, SCH was not an independent risk factor for PCOS after adjusting for confounding factors (OR = 0.984, 95% CI 0.581-1.667). For the first time, our results suggest that SCH does not increase the risk of PCOS in obese women of reproductive age.

Effect of Weight Loss after Bariatric Surgery on Thyroid-Stimulating Hormone Levels in Patients with Morbid Obesity and Normal Thyroid Function

BACKGROUND

Several studies have reported that morbid obesity is associated with increased thyroid-stimulating hormone (TSH) levels. However, it is not clear what is the impact of bariatric surgery on postoperative thyroid function. The aim of this study was to evaluate the effect of weight loss after bariatric surgery on TSH levels in euthyroid patients with morbid obesity.

METHODS

We performed a retrospective observational study of 949 euthyroid patients (86.1% female; age 42.0 ± 10.3 years, BMI 44.3 ± 5.7 kg/m²) with morbid obesity submitted to bariatric surgery (laparoscopic adjustable gastric band, Roux-en-Y gastric bypass, or sleeve gastrectomy). Patients were subdivided in two groups: normal TSH group (TSH <2.5 mU/L) and high-normal TSH group (TSH ≥2.5 mU/L). The impact of anthropometric parameters, comorbidities, TSH, free thyroxine (FT4), free triiodothyronine (FT3), type of surgery, and excessive body weight loss (EBWL) on TSH variation 12 months after surgery was evaluated.

RESULTS

The high-normal TSH group (24.3% of patients) included more women, presented a higher BMI, higher systolic blood pressure, and higher FT3 levels. There was a significant decrease of TSH 12 months after surgery that was more marked in the high-normal TSH group (normal TSH group: 1.57 ± 0.49 to 1.53 ± 0.69 mIU/L, p = 0.063; high-normal TSH group: 3.23 ± 0.59 to 2.38 ± 0.86 mIU/L, p < 0.001). In a multivariate analysis, after adjusting for relevant covariates, EBWL, baseline BMI, and baseline FT3 were significantly associated with TSH decrease 12 months after bariatric surgery.

CONCLUSION

Bariatric surgery promotes a decrease of TSH that is significantly greater in patients with high-normal TSH and is independently associated with EBWL after surgery.

Preoperative thyroid function and weight loss after bariatric surgery

Thyroid function has an important role on body weight regulation. However, the impact of thyroid function on weight loss after bariatric surgery is still largely unknown. We evaluated the association between preoperative thyroid function and the excess weight loss 1 year after surgery, in 641 patients with morbid obesity who underwent bariatric surgery. Patients with a history of thyroid disease, treatment with thyroid hormone or antithyroid drugs and those with preoperative evaluation consistent with overt hypothyroidism or hyperthyroidism were excluded. The preoperative levels of TSH and FT4 were not associated with weight loss after bariatric surgery. The variation of FT3 within the reference range was also not associated with weight loss. In contrast, the subgroup with FT3 above the reference range (12.3% of patients) had a significantly higher excess weight loss than patients with normal FT3. This difference remained significant after adjustment for age, sex, BMI, type of surgery, TSH and FT4. In conclusion, we observed an association between high FT3 and a greater weight loss after bariatric surgery, highlighting a group of patients with an increased benefit from this intervention. Our results also suggest a novel hypothesis: the pharmacological modulation of thyroid function may be a potential therapeutic target in patients undergoing bariatric surgery.

Effect of Bariatric Surgery on Thyroid Function in Obese Patients: a Systematic Review and Meta-Analysis

We aimed to make a meta-analysis regarding the effect of bariatric surgery on thyroid function in obese patients. PubMed, EMBASE, CENTRAL, and four Chinese databases were searched for clinical studies. Data were pooled using Review Manager 5.3, and subgroup and sensitivity analyses were performed if necessary and feasible. As a result, 24 articles were included into meta-analysis. Bariatric surgery was associated with significant decrease in TSH, FT3, and T3 levels. However, FT4, T4, and rT3 levels were not significantly changed postoperatively. In addition, bariatric surgery had a favorable effect on overt and subclinical hypothyroid, with reduction of thyroid hormone requirements postoperatively. In conclusion, TSH, FT3, and T3 decrease are expected following bariatric surgery, as well as non-significant change of T4, FT4, and rT3 levels.

Thyroid stimulating hormone exhibits the impact on LDLR/LDL-c via up-regulating hepatic PCSK9 expression

CONTEXT

Thyroid stimulating hormone (TSH) has received increasing attention as being closely associated with increased low-density lipoprotein cholesterol (LDL-c) level and higher atherosclerotic risks. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is known for increasing circulating LDL-c level by inducing LDL receptor degradation. However, whether TSH influences hepatic PCSK9 expression and LDL-c metabolism remains unclear.

METHODS

First, the correlation between TSH and lipid profiles were investigated in euthyroid population and in subclinical hypothyroidism patients. Then, an in vitro study was conducted to validate the effects of TSH on hepatic PCSK9 expression in HepG2 cells.

RESULTS

Serum TSH concentrations positively correlated with LDL-c levels in euthyroid subjects. Subclinical hypothyroidism patients with higher serum TSH levels showed significantly increased serum PCSK9 levels than the matched euthyroid participants (151.29 (89.51-293.03) vs. 84.70 (34.98-141.72) ng/ml, P<0.001), along with increased LDL-c concentrations. In HepG2 cells, LDLR expression on the plasma membrane was decreased, and PCSK9 mRNA and protein levels were synchronously upregulated after recombinant human TSH (rhTSH) treatment, while the effects could be blocked by TSH receptor blocking antibody K1-70. Sterol regulatory element binding protein (SREBP) 1c and SREBP2 mRNA expressions were enhanced after rhTSH treatment, and specific siRNAs significantly inhibited the effects of rhTSH. Furthermore, there was a noticeable induction of PCSK9 expression by rhTSH even though HMGCR gene expression was silenced.

CONCLUSION

We conclude a regulating role of TSH on hepatic PCSK9 expression, which further contributing to a higher LDL-c level.

Reference values for TSH may be inadequate to define hypothyroidism in persons with morbid obesity: Di@bet.es study

OBJECTIVE

To analyze the reference range of thyroid-stimulating hormone (TSH) in different BMI categories and its impact on the classification of hypothyroidism.

METHODS

The study included 3,928 individuals free of thyroid disease (without previous thyroid disease, no interfering medications, TSH <10 µUI/mL and thyroid peroxidase antibodies [TPO Abs] <50 IU/mL) who participated in a national, cross-sectional, population-based study and were representative of the adult population of Spain. Data gathered included clinical and demographic characteristics, physical examination, and blood and urine sampling. TSH, free thyroxine, free triiodothyronine, and TPO Ab were analyzed by electrochemiluminescence (E170, Roche Diagnostics, Basel, Switzerland).

RESULTS

The reference range (p2.5-97.5) for TSH was estimated as 0.6 to 4.8 µUI/mL in the underweight category (BMI<20 kg/m² ), 0.6 to 5.5 µUI/mL in the normal-weight category (BMI 20-24.9 kg/m² ), 0.6 to 5.5 µUI/mL in the overweight category (BMI 25-29.9 kg/m² ), 0.5 to 5.9 µUI/mL in the obesity category (BMI 30-39.9 kg/m² ), and 0.7 to 7.5 µUI/mL in the morbid obesity category (BMI ≥40). By using the reference criteria for the normal-weight population, the prevalence of high TSH levels increased threefold in the morbid obesity category (P < 0.01).

CONCLUSIONS

Persons with morbid obesity might be inappropriately classified if the standard ranges of normality of TSH for the normal-weight population are applied to them.

Thyroid Function and High-Sensitivity C-Reactive Protein in Cross-Sectional Results from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil): Effect of Adiposity and Insulin Resistance

BACKGROUND

Subclinical hypothyroidism (SCH) is associated with an increased cardiovascular risk, but little information is available about its association with high-sensitivity C-reactive protein (hs-CRP).

OBJECTIVES

This study aims to analyze the association between SCH and hs-CRP using baseline data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).

METHODS

The study has a cross-sectional design. We included subjects with normal thyroid function (thyroid-stimulating hormone, TSH, 0.4-4.0 μIU/ml and normal free thyroxine, fT₄, 10.3-24.45 pmol/l) and SCH (TSH >4.0 μIU/ml and normal fT₄) who were evaluated for hs-CRP. We excluded individuals on medications that affect thyroid function and those who had prevalent cardiovascular disease. Multivariate linear regression evaluated hs-CRP and TSH as continuous variables, and logistic regression models assessed hs-CRP ≥19.05 nmol/l as the dependent variable and crescent quintiles of TSH as the independent variables adjusted for demographic and cardiovascular risk factors.

RESULTS

We included 12,284 subjects with a median age of 50 years (interquartile range = 45-57); 6,408 (52.2%) were female, 11,589 (94.3%) were euthyroid, and 695 (5.7%) had SCH. Bivariate analyses of participants stratified into quintiles of TSH revealed differences according to hs-CRP but not the Framingham risk score. The fifth quintile of TSH was not associated with elevated hs-CRP, odds ratio = 1.11 (95% confidence interval = 0.98-1.26), p = 0.102, in a fully adjusted logistic model, also consistent with the linear model (β = 0.024, p = 0.145).

CONCLUSIONS

TSH is not associated with hs-CRP. Obesity and insulin resistance are very important confounders in the study of the association between SCH and hs-CRP.