Thyroid Function in Korean Adolescents with Obesity: Results from the Korea National Health and Nutrition Examination Survey VI (2013-2015)

Thyrotropin and body mass index, are they related?

OBJECTIVES

It is well recognized that overt thyroid dysfunction is associated with changes in body mass index (BMI). However, there is ongoing debate regarding the influence of thyroid stimulating hormone (TSH) on BMI, in euthyroid subjects. The aim of this study is to examine the association of TSH with BMI in an outpatient population without evidence of thyroid disease.

METHODS

Cross-sectional study conducted in an Endocrinology Department. We identified the latest TSH and BMI measurements in 923 patients from the reference euthyroid population. All patients with positive thyroid autoimmunity and nodules were excluded. We performed a linear regression analysis using SPSSv.025.

RESULTS

923 adult patients were evaluated. 79.4% were males, with a mean age of 67.6 years old. Mean TSH level was 1.78 mIU/L and mean BMI was 29.2 kg/m². A significant negative correlation between serum TSH concentration and BMI was evident (p=0.04; r=-0.067). Statistical significance was lost when performing subgroup analysis, for males and females (p=0.19 and p=0.075), elderly (≥65 years) and non-elderly (p=0.55 and p=0.32) and also obese (BMI ≥30 kg/m²) and non-obese (p=0.39 and p=0.13).

CONCLUSIONS

The relationship between BMI and TSH is not consensual in the literature. This study included a large cohort sample of euthyroid patients, majority men and with negative autoimmunity. Our results support the hypothesis that variation in thyroid status within the normal range, could have a negative effect on BMI, contrary to most published studies.

Obesity is associated with subclinical hypothyroidism in the presence of thyroid autoantibodies: a cross-sectional study

BACKGROUND

Both obesity and subclinical hypothyroidism (SCH) have adverse effects on human body, but the relationship between these two conditions remains inconsistent. The presence of thyroid autoantibodies influences thyroid hormone levels, and may further mediate the interaction between obesity and SCH. This study aimed to explore the association among obesity, SCH and thyroid autoantibodies.

METHODS

This study was a cross-sectional survey of 2505 subjects. Obesity was defined as a body mass index ≥28 kg/m². Serum concentrations of thyroid hormones, thyroid peroxidase antibody (TPO-Ab) and thyroglobulin antibody (Tg-Ab) were examined. Logistic analysis was used to explore the relation among obesity, SCH and thyroid autoantibodies.

RESULTS

A proportion of 11.54% (289/2505) subjects were obese, and 165 subjects had SCH. The positive rates of thyroid autoantibodies, TPO-Ab and Tg-Ab were 17.64% (442/2505), 11.02% (276/2505) and 14.13% (354/2505), respectively. The proportion of SCH was significantly higher in obese than nonobese subjects among those with positive thyroid autoantibodies [22.41% (13/58) vs. 11.72% (45/384), p = 0.025, χ2 test]. Moreover, obesity was significantly associated with SCH in the presence of thyroid autoantibodies after adjusting for confounding factors (OR 2.212, 95% CI 1.103 to 4.433, p = 0.025). A higher proportion of subjects with obesity had Tg-Ab positivity [17.99% (52/289) vs. 13.63% (302/2216), p = 0.045, χ2 test], and obesity remained significantly associated with Tg-Ab positivity by multiple logistic analysis (OR 1.504, 95% CI 1.077 to 2.101, p = 0.017).

CONCLUSIONS

Obesity was associated with SCH in the presence of thyroid autoantibodies. Examination of SCH is recommended in obese subjects with thyroid autoantibody positivity.

The relationship between overweight and thyroid function in first-episode, untreated Chinese patients with major depressive disorder with different ages of onset

BACKGROUND

Major depressive disorder (MDD) and obesity are common. There are many differences in many aspects of MDD patients at different ages of onset (AOO); however, there are currently no studies on differences in obesity or overweight. This study aims to evaluate whether thyroid function changes with body weight, and to explore the related factors of overweight in MDD patients with different AOOs.

METHODS

A total of 1716 first-episode, untreated Chinese Han outpatients with MDD were recruited from a general hospital. Hamilton Anxiety Scale (HAMA), Hamilton Depression Scale (HAMD) and Positive Symptom subscale of the Positive and Negative Syndrome Scale (PANSS) were used to evaluate anxiety, depression and psychotic symptoms, respectively. The participants were divided into two groups: early adulthood onset (EAO, <45 years old) and mid-adulthood onset (MAO, >=45 years old).

RESULTS

Compared with EAO patients, MAO patients scored higher on the HAMD, HAMA, CGI-S and PANSS positive symptoms subscale, and they also had higher systolic and diastolic blood pressure (BP), higher serum levels of thyroid stimulating hormone (TSH), FBG, cholesterol (TC) and low-density lipoprotein, but they had lower serum levels of free triiodothyronine 3 and high-density lipoprotein. TSH, anti-thyroglobulin (TgAb), TC and systolic BP were correlated with overweight in MAO patients, while TSH and FBG were correlated with overweight of EAO patients.

CONCLUSIONS

The results indicate that TSH is related to overweight in both AOO subgroups, and the influencing factors of overweight related to thyroid function may be different in different AOOs.

Causal Association Between Serum Thyrotropin and Obesity: A Bidirectional, Mendelian Randomization Study

CONTEXT

The association between serum thyrotropin (TSH) and obesity traits has been investigated previously in several epidemiological studies. However, the underlying causal association has not been established.

OBJECTIVE

This work aimed to determine and analyze the causal association between serum TSH level and obesity-related traits (body mass index [BMI] and obesity).

METHODS

The latest genome-wide association studies (GWASs) on TSH, BMI, and obesity were searched to obtain full statistics. Bidirectional 2-sample mendelian randomization (MR) was performed to explore the causal relationship between serum TSH and BMI and obesity. The inverse variance-weighted (IVW) and MR-Egger methods were used to combine the estimation for each single-nucleotide variation (formerly single-nucleotide polymorphism). Based on the preliminary MR results, free thyroxine (fT4) and free 3,5,3'-triiodothyronine (fT3) levels were also set as outcomes to further analyze the impact of BMI on them. BMI and obesity were treated as the outcomes to evaluate the effect of serum TSH on them, and TSH was set as the outcome to estimate the effect of BMI and obesity on it.

RESULTS

IVW and MR-Egger results both indicated that genetically driven serum TSH did not causally lead to changes in BMI or obesity. Moreover, the IVW method showed that the TSH level could be significantly elevated by genetically predicted high BMI (β = .038, SE = 0.013, P = .004). In further MR analysis, the IVW method indicated that BMI could causally increase the fT3 (β = 10.123, SE = 2.523, P < .001) while not significantly affecting the fT4 level.

CONCLUSION

Together with fT3, TSH can be significantly elevated by an increase in genetically driven BMI.

Serum Levels of Thyroid Stimulating Hormone and Luteinizing Hormone Are Decreased in Girls with Central Precocious Puberty after 12-Month GnRH Agonist Treatment

Puberty is the transitional period from childhood to adult that leads to growth spurt, sexual maturation and attainment of reproductive capacity. Precocious puberty is defined when secondary sexual characteristics develop before the age of eight for girls and nine for boys. Central precocious puberty (CPP) is diagnosed when the process is driven by premature activation of hypothalamic gonadotropin-releasing hormone (GnRH) secretion. Many factors promote CPP, and the thyroid function is thought to be one of them. In our previous study, thyroid stimulating hormone (TSH) was higher in the CPP group than that of the participants without CPP. This elevation of TSH in CPP is said to be associated with pubertal luteinizing hormone (LH) elevation. The aim of this study was to evaluate the causal relationship between TSH and LH in CPP patients. A total of 221 girls diagnosed with CPP and treated with GnRH agonists were included. All participants except one showed LH suppression (peak LH < 3 IU/L), and serum levels of follicle stimulating hormone (FSH) were also lower after the treatment. These results indicate that puberty has slowed down and that the patients were successfully treated for CPP. As for thyroid hormones, TSH was significantly lower and free thyroxine (fT4) levels were higher after 12 months of GnRH agonist treatment compared with baseline. With GnRH agonist treatment, the serum levels of LH and TSH were decreased, suggesting that the increase in serum TSH levels is associated with premature LH elevation in girls with CPP.

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.

Thyroid function in girls with central precocious puberty

PURPOSE

Obesity is a well-known risk factor for central precocious puberty (CPP). Recently, elevated thyroid stimulating hormone (TSH) was reported in obese youth. However, few data regarding the relationship between CPP and TSH are available. The aim of this study was to evaluate thyroid function in girls with CPP and the relationship between CPP and serum TSH concentration.

METHODS

This was a retrospective cross-sectional study. A total of 1,247 girls aged between 6.0 and 8.9 years who had undergone a gonadotropin-releasing hormone (GnRH) stimulation test to determine the presence of puberty were studied. Subjects were classified into CPP (n=554) and non-CPP (n=693) groups according to the results of the GnRH stimulation test. Characteristics and laboratory data of the CPP and non-CPP groups were compared and correlations between those characteristics and laboratory data and TSH concentration were evaluated. Serum TSH concentration in the CPP group was higher than that of the non-CPP group (3.19±1.55 mIU/L vs. 2.58±1.34 mIU/L, P&lt;0.001).

RESULTS

Serum free thyroxine (fT4) concentration in the CPP group was notably lower than that of the non-CPP group (1.38±0.14 ng/dL vs. 1.44±0.18 ng/dL, P&lt;0.001). Across all subjects, 149 girls (11.9%) had hyperthyrotropinemia. The prevalence of hyperthyrotropinemia was higher in the CPP group compared to the non-CPP group (15.7% vs. 8.9%, P&lt;0.001). TSH concentrations were positively correlated with age, height, weight, BMI, bone age, bone age advance, insulin-like growth factor 1 (IGF-1), IGF-1 standard deviation score, basal luteinizing hormone (LH), peak LH and basal follicle-stimulation hormone. TSH concentrations were negatively correlated with fT4. Multiple linear regression analysis showed that age (β=0.548, P&lt;0.001) and peak LH (β=0.019, P=0.008) were independently associated with serum TSH concentration.

CONCLUSION

Hyperthyrotropinemia in girls with CPP tends to be associated with pubertal LH elevation. In conclusion, pubertal onset may be associated with thyroid function.

Effects of thyroid hormone and depression on common components of central obesity

Objective

We investigated the prevalence of abnormal thyroid function and depression in centrally obese participants, and to analyze the relationship of thyroid hormones and depression with components of central obesity.

Methods

We randomly selected 858 centrally obese participants and 500 non-obese controls in this study. For all participants, we measured serum free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), body mass index (BMI), waist–hip ratio (WHR), fasting blood glucose and insulin, homeostasis model assessment of insulin resistance (HOMA-IR), lipid concentrations, and blood pressure. Depression was assessed using the Center for Epidemiological Studies-Depression (CES-D) scale.

Results

Centrally obese participants had a higher prevalence of hypothyroidism and depression than non-obese controls. Serum FT4 levels negatively correlated with BMI and serum TSH levels and positively correlated with BMI, WHR, total triglycerides (TG), total cholesterol (TC), and low density lipoprotein cholesterol (LDL-C). After excluding participants with hypothyroidism and hyperthyroidism, serum FT4 levels showed negative correlation and serum TSH levels showed positive correlation with BMI in the remaining centrally obese participants. CES-D scores positively correlated with BMI.

Conclusion

We found high prevalences of hypothyroidism and depression among centrally obese participants. FT4 and TSH are important in weight regulation. Depression positively correlated with obesity.