Association between thyrotropin levels and insulin sensitivity in euthyroid obese adolescents

Thyroid-Stimulating Hormone Levels within the Trimester-Specific Reference Intervals Are Correlated with Non-High-Density Lipoprotein Cholesterol and Remnant Cholesterol Concentrations in Pregnant Women

OBJECTIVE

Thyroid-stimulating hormone (TSH) levels are associated with serum lipid concentrations in the general nonpregnant population. Here, we aimed to establish trimester-specific reference intervals and to explore the associations of their variations within the specific reference intervals during pregnancy.

METHODS

Trimester-specific reference intervals were established according to the Clinical and Laboratory Standard Institute EP28-A3c guidelines using a direct sampling method based on a large prospective cohort. After making one-to-one matches, correlation analyses between TSH and lipid index levels, especially within the reference intervals, were conducted.

RESULT

A total of 1648 pregnant women for TSH and 2045 subjects for lipids were recruited to establish the trimester-specific reference intervals. The upper reference limit (90% confidence interval) of TSH for pregnant women in the first trimester is 3.95 (3.66-4.29) mIU/L, which is very close to the default value (4.0 mIU/L) recommended by the American Thyroid Association in 2017. Apart from triglyceride and high-density lipoprotein cholesterol, TSH levels were positively associated with the serum concentrations of total cholesterol, low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol (non-HDL-C), and remnant cholesterol (RC) either in the entire range or within the specific reference intervals. Of note, the positive correlations between TSH and non-HDL-C and RC were, albeit similarly weak (r < 0.25), relatively more robust (P < .001).

CONCLUSION

In this study, we showed positive correlations between TSH and lipid components within trimester-specific reference intervals, highlighting the need for the integrated management of pregnant women over age 35 and with nonoptimal lipid status in China.

Prevalence and clinical profile of abnormal glucose in first-episode and drug-naïve patients with major depressive disorder with comorbid abnormal thyroid function: a large-scale cross-sectional study

BACKGROUND

The associated factors of abnormal glucose in patients with major depressive disorder (MDD) with comorbid abnormal thyroid function (ATF) remain unclear. To the best of our knowledge, this is the first study with a large sample size that examines the risk factors of abnormal glucose in first-episode drug-naïve (FEDN) MDD patients comorbid with ATF and includes clinical correlates and thyroid hormone levels.

METHODS

A total of 1718 FEDN MDD patients were recruited. The Hamilton Depression Scale (HAMD), Hamilton Anxiety Scale (HAMA), and Positive and Negative Syndrome Scale (PANSS) positive subscale were used to evaluate the symptoms of patients. Fasting blood glucose concentration and thyroid hormone levels were measured.

RESULTS

The prevalence of abnormal glucose in MDD patients with comorbid ATF was 47.3%, which was 4.25 times higher than that in MDD patients without ATF (17.4%). Compared to those ATF patients without abnormal glucose, ATF patients with abnormal glucose scored higher on HAMD, HAMA and PANSS positive subscale, had a higher rate of suicide attempts, severe anxiety and psychotic symptoms, and had higher levels of thyroid-stimulating hormone (TSH), and thyroid peroxidases antibody (TPOAb) which were also correlated with abnormal glucose in MDD patients comorbid ATF (all P < 0.05). The combination of HAMD score and TSH could differentiate abnormal glucose from ATF. Further, TSH was independence-related with the concentration of fasting blood glucose in MDD patients with comorbid ATF.

CONCLUSION

Our results demonstrate a high prevalence of abnormal glucose in MDD patients with comorbid ATF. Some clinical and thyroid function-related variables may be associated with abnormal glucose in MDD patients with comorbid ATF.

Effects of Anterior Pituitary Adenomas' Hormones on Glucose Metabolism and Its Clinical Implications

Pituitary adenomas have recently become more common and their incidence is increasing yearly. Functional pituitary tumors commonly secrete prolactin, growth hormones, and adrenocorticotropic hormones, which cause diseases such as prolactinoma, acromegaly, and Cushing's disease, but rarely secrete luteinizing, follicle-stimulating, thyroid-stimulating, and melanocyte-stimulating hormones. In addition to the typical clinical manifestations of functional pituitary tumors caused by excessive hormone levels, some pituitary tumors are also accompanied by abnormal glucose metabolism. The effects of these seven hormones on glucose metabolism are important for the treatment of diabetes secondary to pituitary tumors. This review focuses on the effects of hormones on glucose metabolism, providing important clues for the diagnosis and treatment of related diseases.

Short-term Changes in Thyroid-Stimulating Hormone Level after Body Fat Reduction via Partial Meal Replacement

BACKGROUND

Serum thyroid-stimulating hormone (TSH) levels change during body weight reduction. However, the changes that occur during short-term body weight control interventions remain controversial. Thus, this study aimed to evaluate the changes in TSH levels according to body fat reduction.

METHODS

We performed a 3-month intervention study involving partial meal replacement. Forty-nine participants completed the study. Correlations between changes in TSH levels and other body composition parameters were determined. The subjects were divided into two groups according to their body fat reduction (>1 kg, n=20; <1 kg, n=29). The changes in metabolic parameters, including TSH levels, were compared. For significant values, a multivariate analysis was performed after adjustment to evaluate the relationship between TSH changes and body fat reduction.

RESULTS

The 3-month intervention caused favorable changes in body proportions and metabolic parameters. TSH levels changed significantly only after changes in total body fat, showing a partial correlation. Changes in TSH levels were significantly different between groups (P=0.014). Moreover, the change in TSH levels was significantly different after adjustment (P=0.012).

CONCLUSION

A body fat reduction, especially >1 kg, can reduce serum TSH concentrations in subjects with metabolic syndrome after short-term body weight intervention.

The Relationship between Thyroid-Stimulating Hormone and Insulin Resistance in Incipient Elderly Type 2 Diabetics with Normal Thyroid Function

Objective

To explore correlations between serum thyroid-stimulating hormone (TSH) concentration within the normal range and insulin resistance and its possible mechanism in incipient type 2 diabetes in elderly patients.

Methods

453 elderly patients with type 2 diabetes were divided into four groups by the quartile of TSH. Body mass index (BMI), waist-to-hip ratio (WHR), fasting plasma glucose (FPG), fasting insulin (FINS), homeostasis model assessment of insulin resistance (HOMA-IR) and homeostasis model assessment of insulin secretion (HOMA-β), blood lipids, and other indicators were compared among all groups, and correlation and regression analysis were conducted. 3T3-L1 preadipocytes were induced into mature adipocytes in vitro, and different concentrations of bovine TSH were used to stimulate adipocytes. The levels of TNF-α in the culture medium were detected by ELISA.

Results

(1) With the increase of TSH, TC showed an increasing trend. Compared with the G1 group (4.80 ± 1.08), G2 group (5.13 ± 1.16), G3 group (5.14 ± 1.39), and G4 group (5.38 ± 1.16), the difference was statistically significant (P < 0.05 or P < 0.01). The LDL also showed an increasing trend. Compared with the G4 group (3.47 ± 0.89), the G1 (3.12 ± 0.82) and G2 groups (3.14 ± 1.05) had a lower LDL, and the difference was statistically significant (P < 0.01). The BMI increased between the G4 group (26.7 ± 3.97) and the G1 group (25.6 ± 3.54), and the difference was statistically significant (P < 0.05). (2) The serum TSH level was positively correlated with FPG, FINS, HOMA-IR, TC, and LDL (R = 0.292, 0.271, 0.394, 0.195, and 0.178, all P < 0.01). (3) TSH is the dependent variable, other indicators are independent variables, and multiple stepwise regression analysis is performed; the results show that only HOMA-IR, TC, and LDL enter the regression equation. (4) The TSH stimulated TNF-α secretion of 3T3-L1 adipocytes in a dose-dependent manner.

Conclusion

The TSH level was positively correlated with the insulin resistance and LDL in the elderly incipient type 2 diabetic patients. Higher levels of TSH may be involved in the development of insulin resistance in the elderly incipient type 2 diabetic patients.

Association of thyroid hormone with body fat content and lipid metabolism in euthyroid male patients with type 2 diabetes mellitus: a cross-sectional study

BACKGROUND

This study aimed to explore the associations of thyroid hormones with body fat content and lipid metabolism in euthyroid male patients with type 2 diabetes mellitus (T2DM).

METHODS

In January 2017, a cross sectional study, 66 male patients with T2DM who met the World Health Organization diagnostic criteria of 1999 who were ≥ 18.0 years and had normal thyroid function were recruited at a tertiary hospital. The categories of thyroid hormones (free triiodothyronine [FT3], free thyroxine [FT4], and thyroid-stimulating hormone [TSH]) were divided into three groups according to tertiles of thyroid hormones.

RESULTS

The mean FT3, FT4, and TSH of the patients were 2.56 pg/mL, 1.03 ng/dL, and 1.50 μIU/mL, respectively. Increased FT3 were associated with higher body mass index (BMI) (P <  0.001), body fat percentage (BFP) (P = 0.008), visceral fat content (VFC) (P = 0.019), adiponectin (P = 0.037), tumor necrosis factor alpha (TNF-α) (P <  0.001), and interleukin 6 (IL-6) (P = 0.015). There were significant differences among the different FT4 categories for BMI (P = 0.033), waist-hip ratio (WHR) (P = 0.030), low-density lipoprotein cholesterol (LDL-C) (P = 0.014), and IL-6 (P = 0.009). Increased TSH could increase the total cholesterol (TC) (P = 0.005) and high-density lipoprotein cholesterol (HDL-C) (P = 0.010). FT3 was positively correlated with BMI (r = 0.45; P <  0.001), WHR (r = 0.27; P = 0.028), BFP (r = 0.33; P = 0.007), VFC (r = 0.30; P = 0.014), adiponectin (r = 0.25; P = 0.045), TNF-α (r = 0.47; P <  0.001), and IL-6 (r = 0.32; P = 0.008). FT4 was positively correlated with HDL-C (r = 0.26; P = 0.038), LDL-C (r = 0.26; P = 0.036), and adiponectin (r = 0.28; P = 0.023). TSH was positively correlated with TC (r = 0.36; P = 0.003).

CONCLUSION

This study found that the changes in thyroid hormones are associated with various body fat content and lipid metabolism in euthyroid male patients with T2DM.

Does serum TSH level act as a surrogate marker for psychological stress and cardio-metabolic risk among adolescent and young people?

OBJECTIVES

The incidence of metabolic syndrome is increasing even at younger ages. Metabolic syndrome constitutes a group of cardiovascular risk factors that include high cholesterol, triacylglycerol, hyperglycemia, central obesity, etc., which increases the risk of cardiovascular disease, diabetes mellitus, may be even cancer. Indian students enter colleges just after crossing their adolescent age and will be exposed to greater academic stress. Psychological stress or depression is associated with transient change in thyroid hormones level or dysfunction. To explore an association among serum Thyroid Stimulating Hormone (TSH) levels, fT3:fT4 ratio, psychological stress scores, and selected known cardio-metabolic risk markers.

METHODS

Forty first year MBBS students were included. Their demographic, anthropometric variables, and the blood pressure were documented. Serum TSH, fT3, fT4, and salivary cortisol level was quantified. The stress level was assessed using Cohen Perceived Stress Scale Scoring. Data were expressed in mean ± standard deviation. Data (parametric/non-parametric) were compared by Independent unpaired ANOVA or Kruskal Wallis test whichever is appropriate. Spearmen correlation analysis was performed.

RESULTS

Serum TSH and Cohen stress score are negatively correlated (r=-0.152), but serum cortisol showed (r=0.763) a positive correlation. TSH levels and the marks obtained in the summative assessments were negatively correlated and the correlation was not statistically significant.

CONCLUSIONS

The psychological stress is associated with low serum TSH, high cortisol, and poor academic performance in first year MBBS students. Blood pressure, plasma glucose, and anthropometric measures were not associated with the psychological stress.

Good agreement between hyperinsulinemic-euglycemic clamp and 2 hours oral minimal model assessed insulin sensitivity in adolescents

BACKGROUND/OBJECTIVE

Rates of dysglycemia are increasing in youth, secondary to obesity and decreased insulin sensitivity (IS) in puberty. The oral minimal model (OMM) has been developed in order to measure IS using an easy oral glucose load, such as an oral glucose tolerance test (OGTT), instead of an hyperinsulinemic-euglycemic clamp (HE-clamp), a more invasive and time-consuming procedure. However, this model, following a standard 2 hour- OGTT has never been validated in youth, a population known for a different physiologic response to OGTT than adults. Thus, we compared IS measurements obtained from OMM following a 2-hour OGTT to HE-clamp and isotope tracer-assessed tissue IS in adolescents. We also compared the liver/muscle-specific IS from HE-clamp with other liver/muscle-specific IS surrogates following an OGTT previously validated in adults.

METHODS

Secondary analysis of a cross-sectional study. Adolescent girls with (n = 26) and without (n = 7) polycystic ovary syndrome (PCOS) (14.6 ± 1.7 years; BMI percentile 23.3%-98.2%) underwent a 2-hour 75 g OGTT and a 4-phase HE-clamp. OMM IS (Si), dynamic Si (Si^d ) and other OGTT-derived muscle and liver IS indices were correlated with HE-clamp tissue-specific IS.

RESULTS

OMM Si and Si^d correlated with HE-clamp-measured peripheral IS (r = 0.64, P <.0001 and r = 0.73; P <.0001, respectively) and the correlation coefficient trended higher than the Matsuda index (r = 0.59; P =.003). The other tissue-specific indices were poorly correlated with their HE-clamp measurements.

CONCLUSION

In adolescent girls, the 2-hour OMM provided the best estimate of peripheral IS. Additional surrogates for hepatic IS are needed for youth.

Sex, puberty, and ethnicity have a strong influence on growth and metabolic comorbidities in children and adolescents with obesity: Report on 1300 patients (the Madrid Cohort)

BACKGROUND

The capacity to correctly assess insulin resistance and its role in further obesity-associated metabolic derangement in children is under debate, and its determinants remain largely unknown.

OBJECTIVE

We investigated the association of the insulin secretion profile with other metabolic derangements and anthropometric features in children and adolescents with obesity, exploring the role of ethnicity.

PATIENTS AND METHODS

Growth and metabolic features, including fasting insulin levels and insulin secretory profile in an oral glucose tolerance test (OGTT), were analyzed according to ethnicity in 1300 patients with obesity (75.8% Caucasians/19.0% Latinos).

RESULTS

Height and bone age were influenced by sex, ethnicity, and insulinemia. Latino patients had higher insulin (P < .001), but similar glycemia both prepubertally and postpubertally, compared with Caucasians. Type 2 diabetes was uncommon (0.1%). Impaired glucose tolerance was associated to higher age, BMI, uric acid, and triglyceride levels (all P < .05), as was fasting hyperinsulinism. Impaired fasting glucose or HbA1c 5.7% to 6.4% showed no association with further metabolic derangement. A delayed insulin peak in the OGTT was associated to more severe metabolic disturbances.

CONCLUSIONS

Obesity-associated hyperglycemia is unusual in our environment whereas fasting and late postprandial hyperinsulinemia are highly prevalent, with this being influenced by race and closely related with lipid metabolism impairment.

Association of Thyroid-Stimulating Hormone and Thyroid Hormones with Cardiometabolic Risk Factors in Euthyroid Children and Adolescents Aged 10-18 Years: A Population-Based Study

Recent evidence indicates that low-normal thyroid function test results within the reference ranges may be related to increased cardiometabolic risk factors. The current study aimed to evaluate the relationship between thyroid function using thyroid-stimulating hormone (TSH) and free thyroxine (FT4) and cardiometabolic risk factors and the clustering of these risk factors (metabolic syndrome) in euthyroid children and adolescents. A total of 250 euthyroid children and adolescents aged 10-18 years were included using data from the Korea National Health and Nutrition Examination Survey (KNHANES) 2015. In the unadjusted correlation analyses, TSH was positively correlated with glucose (r = 0.172, P = 0.006), hemoglobin A1c (HbA1c) (r = 0.149, P = 0.018), insulin (r = 0.144, P = 0.023), homeostatic model assessment for insulin resistance (HOMA-IR) (r = 0.163, P = 0.010), and triglyceride (TG) (r = 0.155, P = 0.014), whereas FT4 was negatively associated with the waist circumference (WC) standard deviation score (SDS) (r = -0.134, P = 0.035), body mass index (BMI) SDS (r = -0.126, P = 0.046), insulin (r = -0.219, P < 0.001), and HOMA-IR (r = -0.211, P < 0.001). In the multiple linear regression analysis, TSH was positively associated with glucose (β = 1.179, P = 0.021), HbA1c (β = 0.044, P = 0.039), and TG (β = 8.158, P = 0.041) after adjustment for possible confounders. FT4 was negatively associated with serum fasting insulin (β = -5.884, P = 0.017) and HOMA-IR (β = -1.364, P = 0.023) in the multiple linear regression analysis. Boys and girls with elevated glucose levels had a higher adjusted mean TSH level compared to those without elevated glucose levels after controlling for confounding factors in the analysis of covariance (2.16 mIU/L vs 3.88 mIU/L, P = 0.004). Our results suggest that higher TSH and/or lower FT4 levels, even within the reference ranges, may be related to increased cardiometabolic risk factors.

The Impact of Adiposity and Puberty on Thyroid Function in Children and Adolescents

Background: In the context of a worldwide increase in childhood obesity, euthyroid hyperthyrotropinemia has been consistently reported and raises questions about its etiology, its potential metabolic complications, and its management. In this study we analyze the thyroid function with respect to BMI, pubertal status, and sex in children with obesity and discuss our results on an integrative context with the existent data from the literature. Methods: In this case-control study, we compared 389 children and adolescents with obesity to 158 controls. Age, sex, thyroid stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), BMI standard deviation score, and pubertal status were recorded. One factor-analysis of variance (ANOVA) was used with p < 0.05. Results: Mean serum TSH of children with obesity was higher (2.95 ± 1.2 mU/L) compared to normal weight group (2.42 ± 1.43 mU/L) (p < 0.0001). Only in females of both groups, serum TSH, T4, and T3 concentrations were all lower during puberty compared to prepuberty. In prepubertal girls and boys with obesity, a statistically significant correlation between TSH and BMI was found (r = 0.32, p = 0.012 and r = 0.47, p < 0.001, respectively), which is not sustained during puberty. Conclusions: Our results confirm the TSH elevation in children with obesity and indicates that puberty and adiposity have a differential sex-dependent impact on thyroid axis function.

In thyroxine-replaced hypothyroid postmenopausal women under simultaneous calcium supplementation, switch to oral liquid or softgel capsule L-thyroxine ensures lower serum TSH levels and favorable effects on blood pressure, total cholesterolemia and glycemia

PURPOSE

In postmenopausal women under L-T4 therapy, which was subsequently accompanied by calcium carbonate (CC) supplementation taken 6-8 h after tablet L-T4, TSH levels were greater than prior to adding CC. Total cholesterolemia [CHOL], fasting glycemia [FG], systolic and diastolic blood pressure [SBP, DBP] were also greater than baseline. Our aim was to explore the effects of either liquid or softgel capsule L-T4, while maintaining CC ingestion 6-8 h, later on TSH levels, CHOL, FG, SBP, and DBP.

METHODS

We proposed to 50 hypothyroid postmenopausal women under tablet L-T4 therapy, to switch to either liquid or softgel capsule L-T4 at the same daily dose while maintaining CC ingestion 6-8 h later. Sixteen women accepted [group I; liquid (n = 9), capsule (n = 7)], while 34 continued tablet L-T4 [group II, (n = 34)].

RESULTS

After 3 months, in group I, TSH decreased significantly (1.23 ± 0.49 vs. 1.80 ± 0.37 mU/L, P < 0.01), as did FG (80.7 ± 7.9 vs. 83.4 ± 6.3 mg/dL, P < 0.05); CHOL, SBP, and DBP decreased, though insignificantly. In contrast, in group II, TSH, FG, CHOL, SBP increased insignificantly, and DBP increased borderline significantly (69.7 ± 9 vs. 66.3 ± 6.5, P < 0.10). Compared to baseline (before adding CC), in group I, TSH was significantly lower (P < 0.01) and the other indices similar; in group II, TSH, FG, and SBP were significantly higher (P < 0.05), DBP borderline significantly higher (P < 0.10) and CHOL insignificantly higher. Performance of liquid L-T4 and capsule L-T4 was similar.

CONCLUSION

Delaying CC ingestion even by 6-8 h after taking tablet L-T4 is not entirely satisfactory, unlike liquid or softgel L-T4.

L-thyroxine malabsorption due to calcium carbonate impairs blood pressure, total cholesterolemia, and fasting glycemia

PURPOSE

Calcium carbonate was previously shown to interfere with L-thyroxine absorption. To estimate the magnitude of tablet L-thyroxine malabsorption caused by calcium carbonate, with resulting increase in serum thyrotropin (TSH), we performed a cohort study in a referral care center.

METHODS

Fifty postmenopausal hypothyroid L-thyroxine-treated women (age 71.7 ± 5.1 years) who added calcium supplementation (600-1000 mg/day) were considered. They were taking L-thyroxine 45-60 min before breakfast (setting 1). After 4.4 ± 2.0 years from initiation of L-thyroxine therapy, they took calcium supplemaentation within 2 h after L-thyroxine taking (setting 2) for 2.3 ± 1.1 years. Hence, we recommended postponing calcium intake 6-8 h after L-thyroxine (setting 3). We evaluated TSH levels, the prevalence of women with elevated TSH (>4.12 mU/L), total cholesterolemia, fasting glycemia, blood pressure, and the prevalence of hypercholesterolemia, hyperglycemia, and hypertension.

RESULTS

TSH levels were 3.33 ± 1.93 mU/L versus 1.93 ± 0.51 or 2.16 ± 0.54 comparing setting 2 with setting 1 or 3 (P < 0.001, both). In setting 2, 18% women had elevated TSH versus none in setting 1 or 3 (P < 0.01). Total cholesterolemia, fasting glycemia, systolic, and diastolic blood pressure were also significantly higher in setting 2 compared to settings 1 and 3. For every 1.0 mU/L increase within the TSH range of 0.85-6.9 mU/L, total cholesterolemia, glycemia, systolic, and diastolic blood pressure increased by 12.1, 3.12 mg/dL, 2.31, and 2.0 mmHg, respectively.

CONCLUSIONS

Monitoring of hypothyroid patients who ingest medications that decrease L-thyroxine absorption should not be restricted to solely measuring serum TSH.

High-normal serum thyrotropin levels and increased glycemic variability in type 2 diabetic patients

PURPOSE

High-normal thyrotropin (TSH) is related to reduced insulin sensitivity and may contribute to glycemic disorders in diabetes. We investigated the relationship between normal serum TSH levels and glycemic variability in euthyroid type 2 diabetic patients.

METHODS

A total of 432 newly diagnosed type 2 diabetic patients with euthyroid function and normal serum TSH levels were recruited between March 2013 and February 2017. Insulin sensitivity was evaluated by the Matsuda index (ISI_Matsuda) following a 75-g oral glucose tolerance test. Multiple glycemic variability indices, including the mean amplitude of glycemic excursions (MAGE), mean of daily differences (MODD), and standard deviation of glucose (SD), were calculated from glucose data obtained with a continuous glucose monitoring system. Average glucose accessed by 24-h mean glucose (24-h MG) was also calculated.

RESULTS

A normal serum TSH level was positively correlated with MAGE, MODD, SD, and 24-h MG (r = 0.206, 0.178, 0.186, and 0.132, respectively, p < 0.01). After adjusting for somatometric parameters, lipid profiles, ISI_Matsuda, and HbA1c via multiple linear regression analysis, mean differences [B(95% CI)] in MAGE, MODD, SD, and 24-h MG between the patients in the lowest and highest quartiles of TSH levels were 0.128(0.031, 0.226), 0.085(0.022, 0.148), 0.039(0.001, 0.078), and 0.002(-0.264, 0.267) mmol/L, respectively. High-normal TSH was independently associated with MAGE, MODD, and SD, but not 24-h MG.

CONCLUSIONS

High-normal serum TSH is a significant additional risk factor for increased glycemic variability in type 2 diabetic patients.

Metabolic syndrome is associated with an increased incidence of subclinical hypothyroidism - A Cohort Study

Prior cross-sectional analyses have demonstrated an association between subclinical hypothyroidism and metabolic syndrome and selected components. However, the temporal relation between metabolic syndrome and declining thyroid function remains unclear. In a prospective study, an unselected cohort of 66,822 participants with and without metabolic syndrome were followed. A proportional hazards regression model was used to estimate hazard ratios (HRs) and 95% CIs for hypothyroidism. Exploratory analyses for the relation between components of metabolic syndrome and declining thyroid function were also undertaken. During an average follow-up of 4.2 years, the incident rates for subclinical hypothyroidism were substantially higher in participants who began the study with metabolic syndrome compared with metabolically normal controls. After controlling for risk factors, patients with metabolic syndrome were at a 21% excess risk of developing subclinical hypothyroidism (adjusted HR 1.21; 95% CI 1.03–1.42). When individual components were analyzed, an increased risk of subclinical hypothyroidism was associated with high blood pressure (1.24; 1.04–1.48) and high serum triglycerides (1.18; 1.00–1.39), with a trend of increasing risk as participants had additional more components. Individuals with metabolic syndrome are at a greater risk for developing subclinical hypothyroidism, while its mechanisms and temporal consequences of this observation remain to be determined.

Subclinical hypothyroidism in childhood - current knowledge and open issues

Subclinical hypothyroidism is defined as serum levels of TSH above the upper limit of the reference range, in the presence of normal concentrations of total T₄ or free T₄. This biochemical profile might be an indication of mild hypothyroidism, with a potential increased risk of metabolic abnormalities and cardiovascular disease recorded among adults. Whether subclinical hypothyroidism results in adverse health outcomes among children is a matter of debate and so management of this condition remains challenging. Mild forms of untreated subclinical hypothyroidism do not seem to be associated with impairments in growth, bone health or neurocognitive outcome. However, ongoing scientific investigations have highlighted the presence of subtle proatherogenic abnormalities among children with modest elevations in their TSH levels. Although current findings are insufficient to recommend levothyroxine treatment for all children with mild asymptomatic forms of subclinical hypothyroidism, they highlight the potential need for assessment of cardiovascular risk among children with this condition. Increased understanding of the early metabolic risk factors associated with subclinical hypothyroidism in childhood will help to improve the management of affected individuals.

Thyrotropin Levels Are Associated with Cardiometabolic Risk Factors in Euthyroid Adolescents

BACKGROUND

Increased thyrotropin (TSH) levels and free triiodothyronine to free thyroxine (fT3:fT4) ratios, even within the euthyroid range, have been associated with cardiometabolic risk factors in adults but are less characterized in youth. This study sought to determine relations between TSH, thyroid hormones, and cardiometabolic risk factors in euthyroid adolescents.

METHODS

Data were extracted from the United States National Health and Nutrition Examination Survey, 2007-2010, for univariate and multivariate analyses of TSH, thyroid hormones, body mass index (BMI), blood pressure, lipids, and glucose metabolism. Subjects aged 12-18 years, with normal TSH and antithyroid peroxidase antibody levels, and without a history of thyroid disease, diabetes, or treatment of hypertension/dyslipidemia (n = 1167) were included. TSH and thyroid hormones were assessed for impact on BMI Z-score, systolic blood pressure (SBP) diastolic blood pressure, total cholesterol (TC), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, triglycerides, and glucose metabolism.

RESULTS

Univariate analyses revealed positive linear relations between TSH and SBP, TC, fasting and two-hour glucose, and homeostasis model assessment of insulin resistance (HOMA-IR). The fT3:fT4 ratio negatively correlated with high-density lipoprotein cholesterol but positively with BMI Z-score, SBP, triglycerides, fasting and two-hour glucose, fasting insulin, and HOMA-IR. In multivariate analyses controlling for age, sex, race/ethnicity, and BMI Z-score, relations between TSH and both TC and fasting glucose remained significant, and the fT3:fT4 ratio was positively associated with fasting glucose and HOMA-IR.

CONCLUSIONS

In an unselected population of euthyroid U.S. adolescents, TSH and thyroid hormones correlate with multiple cardiometabolic risk factors, with age- and sex-independent effects on cholesterol and glucose metabolism.