Thyroid Function in Obese Children and Adolescents

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Abstract

Objective: Obesity is frequently associated with modifications of thyroid size and function. We evaluated the prevalence of thyroid function abnormalities and the effects of puberty and weight loss in obese children and adolescents. Methods: We examined 468 obese children (255 girls and 213 boys aged 3.7–17.9 years) and 52 normal-weight age-matched children as controls. TSH, fT3, fT4, fasting serum insulin and glucose were measured at baseline. fT3, fT4 and TSH were also measured after 6 months of lifestyle intervention in a subset of 43 patients. Results: 109 obese children showed abnormal circulating thyroid hormone concentrations (84 had elevated fT3 levels, 15 elevated TSH, 6 elevated fT4, 3 elevated fT3 and TSH, and 1 elevated fT3, fT4 and TSH levels). Serum TSH and fT3 concentrations were positively correlated with BMI-SDS. The prevalence of patients with abnormal thyroid hormone concentrations was similar between sexes and between prepubertal and pubertal subjects. After 6 months of lifestyle intervention, thyroid hormone concentrations normalized in 27 of the patients with decreased BMI-SDS, and in 2 patients in whom BMI-SDS increased. Conclusions: In obese children, an increased fT3 concentration is the most frequent thyroid function abnormality. Serum fT3 and TSH correlate with BMI. Moderate weight loss frequently restores these abnormalities.

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Most cited references 19

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Thermogenic mechanisms and their hormonal regulation.

J. Silva (2006)

Increased heat generation from biological processes is inherent to homeothermy. Homeothermic species produce more heat from sustaining a more active metabolism as well as from reducing fuel efficiency. This article reviews the mechanisms used by homeothermic species to generate more heat and their regulation largely by thyroid hormone (TH) and the sympathetic nervous system (SNS). Thermogenic mechanisms antecede homeothermy, but in homeothermic species they are activated and regulated. Some of these mechanisms increase ATP utilization (same amount of heat per ATP), whereas others increase the heat resulting from aerobic ATP synthesis (more heat per ATP). Among the former, ATP utilization in the maintenance of ionic gradient through membranes seems quantitatively more important, particularly in birds. Regulated reduction of the proton-motive force to produce heat, originally believed specific to brown adipose tissue, is indeed an ancient thermogenic mechanism. A regulated proton leak has been described in the mitochondria of several tissues, but its precise mechanism remains undefined. This leak is more active in homeothermic species and is regulated by TH, explaining a significant fraction of its thermogenic effect. Homeothermic species generate additional heat, in a facultative manner, when obligatory thermogenesis and heat-saving mechanisms become limiting. Facultative thermogenesis is activated by the SNS but is modulated by TH. The type II iodothyronine deiodinase plays a critical role in modulating the amount of the active TH, T(3), in BAT, thereby modulating the responses to SNS. Other hormones affect thermogenesis in an indirect or permissive manner, providing fuel and modulating thermogenesis depending on food availability, but they do not seem to have a primary role in temperature homeostasis. Thermogenesis has a very high energy cost. Cold adaptation and food availability may have been conflicting selection pressures accounting for the variability of thermogenesis in humans.

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Hyperthyrotropinemia in obese children is reversible after weight loss and is not related to lipids.

Werner Andler, Thomas Reinehr, Gideon de Sousa (2006)

There is some controversy whether T(4) treatment is indicated in obese humans with hyperthyrotropinemia. The objective of this study was to examine whether hyperthyrotropinemia is a cause or a consequence of obesity. The study was designed as a cross-sectional comparison between obese and lean children and includes a 1-yr follow-up study. The study was set in a primary care facility. The patients were 246 obese and 71 lean children. The 1-yr intervention program was based on exercise, behavior therapy, and nutrition education. The main outcome measures were TSH, free T(3) (fT3), free T(4) (fT4), high-density lipoprotein, low-density lipoprotein, and total cholesterol at baseline and 1 yr later. TSH (P = 0.009) and fT3 (P = 0.003) concentrations were significantly higher in obese children than in normal weight children, whereas there was no difference in fT4 levels (P = 0.804). Lipids did not correlate significantly to thyroid hormones in cross-sectional and longitudinal analyses. fT3, fT4, and lipids did not differ significantly in the 43 (17%) children with TSH levels above the normal range from the children with TSH levels within the normal range. Substantial weight loss in 49 obese children led to a significant reduction of TSH (P = 0.035) and fT3 (P = 0.036). The 197 obese children without substantial weight loss demonstrated no significant changes of thyroid hormones. Because fT3 and TSH were moderately increased in obese children and weight loss led to a reduction, the elevation of these hormones seems to be rather a consequence of obesity than a cause of obesity. Because fT3 and TSH were both increased in obesity and thyroid hormones were not associated to lipids, we put forward the hypothesis that there is no necessity for thyroxine treatment.

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Relationship of thyroid function with body mass index, leptin, insulin sensitivity and adiponectin in euthyroid obese women.

Frida Leonetti, Maria Ribaudo, Gianluca Iacobellis … (2005)

A possible relationship between thyroid hormones and adipose tissue metabolism in humans has been suggested. Aim of the study We sought to evaluate thyroid function and its possible relationship with body mass index (BMI), leptin, adiponectin and insulin sensitivity in euthyroid obese women. Eighty-seven uncomplicated obese women (mean age 34.7 +/- 9 years, mean BMI 40.1 +/- 7 kg/m(2)) were studied. Levels of TSH, free thyroxine (FT4), free triiodothyronine (FT3), plasma adiponectin and leptin were evaluated. Insulin sensitivity was assessed by euglycaemic hyperinsulinaemic clamp (M index), fasting insulin and HOMA-IR. Uncomplicated obese women with BMI > 40 kg/m(2) showed higher serum TSH than obese subjects with BMI < 40 kg/m(2) (P < 0.01). TSH was correlated with BMI (r = 0.44, P = 0.01) leptin (r = 0.41, P = 0.01), leptin/BMI ratio (r = 0.33, P = 0.03), body surface area (r = 0.26, P = 0.05), HOMA-IR (r = 0.245, P = 0.05) and inversely with adiponectin (r = -0.25, P = 0.05) and M index (r = -0.223 P = 0.05). Our data show that, although thyroid function was normal in the studied obese population, TSH and BMI were positively related. TSH has been found to be correlated also with leptin adjusted for BMI. TSH could represent a marker of altered energy balance in severe, but uncomplicated obese women.

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Author and article information

Journal

Journal ID (publisher-id): HRP

Journal ID (nlm-ta): Horm Res Paediatr

Journal ID (doi): 10.1159/issn.1663-2818

Title: Hormone Research in Paediatrics

Publisher: S. Karger AG

ISSN (Print): 1663-2818

ISSN (Electronic): 1663-2826

Publication date Subscription-year: 2010

Publication date (Print): March 2010

Publication date (Electronic): 03 March 2010

Volume: 73

Issue: 3

Pages: 193-197

Affiliations

Servizio di Endocrinologia Pediatrica, Ospedale Regionale per le Microcitemie, Cagliari, Italy

Article

Publisher ID: 284361 Other ID: Horm Res Paediatr 2010;73:193–197

DOI: 10.1159/000284361

PubMed ID: 20197672

SO-VID: 229c5a03-26f4-4894-b47e-4af9950dfba3

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Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

History

Date received : 11 February 2009

Date accepted : 02 April 2009

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Tables: 2, References: 26, Pages: 5

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Thyroid Function in Obese Children and Adolescents

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Abstract

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Karger: Endocrinology

Most cited references 19

Thermogenic mechanisms and their hormonal regulation.

Hyperthyrotropinemia in obese children is reversible after weight loss and is not related to lipids.

Relationship of thyroid function with body mass index, leptin, insulin sensitivity and adiponectin in euthyroid obese women.

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Cited by 28

Most referenced authors 194