Lack of association between peripheral activity of thyroid hormones and elevated TSH levels in childhood obesity

Thyroid hormone levels and BMI-SDS changes in adolescents with obesity

Background

Thyroid hormones play an important role in energy metabolism and weight control, explained mostly by inducing thermogenesis and increasing basal metabolic rate. It has recently been shown that FT4 levels are associated with food preferences, which might also play a role in modulating body weight. The aim of this longitudinal follow-up study was to analyze the relationship of thyroid hormones levels (FT4, TSH) at baseline with weight/BMI-SDS changes in children and adolescents with obesity.

Methods

Three hundred seventy-seven children and adolescents have been enrolled to this study and followed up without a systematic intervention program for 5.59 ± 1.85months. Children and adolescents were divided into three subgroups: 1) 144 adolescents with obesity (15-19 years), 2) 213 children with obesity (10-14.9 years), and 3) 20 lean adolescents (15-19 years). Thyroid hormones were measured at the baseline, and anthropometry was performed at the baseline and during the follow-up. For further analyses, participants were divided according to the BMI-SDS change into two groups: 1. with BMI-SDS decrease, and 2. with BMI-SDS increase.

Results

Adolescents with obesity from the BMI-SDS decrease group had significantly lower baseline serum levels of TSH compared to the BMI-SDS increase group (2.4 ± 1.0 vs. 3.2 ± 2.0mIU/l; p=0.005). Similar difference was found for FT4 levels (14.7 ± 2.2 in the BMI-SDS decrease group vs. 15.5 ± 2.7pmol/l in the BMI-SDS increase group, p=0.048). Moreover, the BMI-SDS decrease was present in significantly higher percentage of adolescents with obesity with lower than median TSH level compared to those with higher than median TSH level at baseline (61.1% vs 38.6%, p=0.011). Likewise, the BMI-SDS decrease was present in significantly higher percentage of adolescent females with obesity and lower than median FT4 compared to those with higher than median FT4 level at baseline (70.6% vs. 23.5%, p<0.001). No associations of baseline thyroid hormones with the BMI-SDS change were observed in children with obesity or lean adolescents.

Conclusion

Adolescents with obesity and increased BMI-SDS during the follow-up had significantly higher baseline levels of both TSH and FT4 compared to BMI-SDS decrease group. These results support the previous findings that higher FT4 in individuals with obesity may influence weight gain.

Thyroid axis hormones and anthropometric recovery of children/adolescents with overweight/obesity: A scoping review

Introduction

Thyroid hormones exert multiple physiological effects essential to the maintenance of basal metabolic rate (BMR), adaptive thermogenesis, fat metabolism, growth, and appetite. The links between obesity and the hormones of the thyroid axis, i.e., triiodothyronine (T3), thyroxine (T4), and thyrotropin (TSH), are still controversial, especially when considering children and adolescents. This population has high rates of overweight and obesity and several treatment approaches, including nutritional, psychological, and physical exercise interventions have been used. Understanding the importance of the hormones of the thyroid axis in the recovery from overweight and obesity may help directing measures to the maintenance of a healthy body composition. The present scoping review was carried out to analyze studies evaluating these hormonal levels throughout interventions directed at treating overweight and obesity in children and adolescents. The main purpose was to ascertain whether the hormones levels vary during weight loss.

Methods

We selected for analysis 19 studies published between 1999 and 2022.

Results

Most of the studies showed that changes in different anthropometric indicators, in response to the multidisciplinary interventions, correlated positively with free T3 (fT3), total T3 (TT3), and TSH. With respect to free T4 (fT4) and total T4 (TT4).

Discussion

The most common finding was of unchanged levels and, hence, no significant association with weight loss. Moreover, thyroxine supplementation has failed to affect the response to the interventions. Further studies are necessary to elucidate the relevance of the variations in hormone levels to the establishment of overweight/obesity and to the recovery from these conditions in children/adolescents.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42020203359.

ASSOCIATIONS OF THYROID VOLUME AND FUNCTION WITH CHILDHOOD OBESITY

CONTEXT

The links between obesity and thyroid function or thyroid volume in children are still controversial with limited available data.

OBJECTIVE

This study aimed to examine thyroid function and volume in obese Turkish school-age children in comparison to normal-weight children.

DESIGN

Cross-sectional study.

SUBJECTS AND METHODS

One hundred obese children (47 boys, 53 girls; mean age 10.34±2.79 years) with a body mass index (BMI) above 95th percentile, and 100 normal-weight children (42 boys, 58 girls; 10.34±2.79 years) were included. The study parameters were BMI z score (Z-BMI), body surface area (BSA), thyroid volume, free thyroxine (fT4) and thyroid stimulating hormone (TSH) levels.

RESULTS

The mean TSH and fT4 levels did not show a significant difference between obese and normal-weight children (p>0.05). The mean thyroid volume was higher in obese children (6.46±5.84 and 4.64±1.44, respectively; p=0.043). fT4 correlated negatively with Z-BMI in both normal-weight and obese children (r=-0.285, p=0.004 and r=-0.289, p=0.004, respectively). Thyroid volume, on the other hand, correlated positively with Z-BMI, again in both normal-weight and obese children (r=0.657, p<0.001 and r=0.444, p<0.001, respectively). Similar associations were found for BSA.

CONCLUSIONS

Thyroid volume correlated positively and fT4 correlated negatively with Z-BMI and BSA, in both obese and normal-weight school-age children, whereas TSH appears to be independent of these parameters.

Fetal over- and undernutrition differentially program thyroid axis adaptability in adult sheep

OBJECTIVE

We aimed to test, whether fetal under- or overnutrition differentially program the thyroid axis with lasting effects on energy metabolism, and if early-life postnatal overnutrition modulates implications of prenatal programming.

DESIGN

Twin-pregnant sheep (n = 36) were either adequately (NORM), under- (LOW; 50% of NORM) or overnourished (HIGH; 150% of energy and 110% of protein requirements) in the last-trimester of gestation. From 3 days-of-age to 6 months-of-age, twin lambs received a conventional (CONV) or an obesogenic, high-carbohydrate high-fat (HCHF) diet. Subgroups were slaughtered at 6-months-of-age. Remaining lambs were fed a low-fat diet until 2½ years-of-age (adulthood).

METHODS

Serum hormone levels were determined at 6 months- and 2½ years-of-age. At 2½ years-of-age, feed intake capacity (intake over 4-h following 72-h fasting) was determined, and an intravenous thyroxine tolerance test (iTTT) was performed, including measurements of heart rate, rectal temperature and energy expenditure (EE).

RESULTS

In the iTTT, the LOW and nutritionally mismatched NORM:HCHF and HIGH:CONV sheep increased serum T₃, T₃:T₄ and T₃:TSH less than NORM:CONV, whereas TSH was decreased less in HIGH, NORM:HCHF and LOW:HCHF. Early postnatal exposure to the HCHF diet decreased basal adult EE in NORM and HIGH, but not LOW, and increased adult feed intake capacity in NORM and LOW, but not HIGH.Conclusions: The iTTT revealed a differential programming of central and peripheral HPT axis function in response to late fetal malnutrition and an early postnatal obesogenic diet, with long-term implications for adult HPT axis adaptability and associated consequences for adiposity risk.

Thyroid Function and Thyroid Autoimmunity in Relation to Weight Status and Cardiovascular Risk Factors in Children and Adolescents: A Population-Based Study

OBJECTIVE

In obese subjects, slight increases have been observed in thyrotropin [thyroid-stimulating hormone (TSH)] levels, but data in children are scarce. The aim of this study was to evaluate whether thyroid function and autoimmunity vary with weight status in a healthy population of children and adolescents and to determine whether hyperthyrotropinemia is associated with any cardiovascular risk factor.

METHODS

This cross-sectional epidemiological study was conducted in Almería (Spain) on a representative sample of 1317 healthy subjects aged 2-16 years. Thyroid function, thyroid autoimmunity and cardiovascular risk factors were measured. Chi-square test, analysis of variance and multiple linear regression were used in the statistical analyses.

RESULTS

The obese children and adolescents had thyrotropin levels (mean ± standard deviation) of 3.12±2.44 mU/L. These levels were higher than those of overweight subjects (2.79±1.51 mU/L) and of normal weight subjects (2.73±1.30 mU/L) (p=0.02). Levels of free thyroxine and urinary iodine did not differ significantly between the groups. The prevalence (95% confidence interval) of thyroid autoimmunity was lower in the individuals with normal weight (2.9%; 2.0-4.2) than in the overweight (6.3%; 3.9-9.9) and obese subjects (5.6%, 2.5-11.3) (p=0.02). TSH levels were associated with obesity (β=0.36; p<0.001) and thyroid autoimmunity (β=1.10; p<0.001). They were not associated with any cardiovascular risk factor.

CONCLUSION

Obese children and adolescents had higher levels of thyrotropin than those who were overweight and of normal weight. The differences among the groups were of very little clinical significance and could possibly be linked to the higher prevalence of thyroid autoimmunity in obese subjects. The hyperthyrotropinemia in these subjects was not associated with any cardiovascular risk factor.