Lean body mass as a determinant of thyroid size

202

185

Obesity and thyroid diseases are common disorders in the general population and they frequently occur in single individuals. Alongside a chance association, a direct relationship between 'thyroid and obesity' has been hypothesized. Thyroid hormone is an important determinant of energy expenditure and contributes to appetite regulation, while hormones and cytokines from the adipose tissue act on the CNS to inform on the quantity of energy stores. A continuous interaction between the thyroid hormone and regulatory mechanisms localized in adipose tissue and brain is important for human body weight control and maintenance of optimal energy balance. Whether obesity has a pathogenic role in thyroid disease remains largely a matter of investigation. This review highlights the complexity in the identification of thyroid hormone deficiency in obese patients. Regardless of the importance of treating subclinical and overt hypothyroidism, at present there is no evidence to recommend pharmacological correction of the isolated hyperthyrotropinemia often encountered in obese patients. While thyroid hormones are not indicated as anti-obesity drugs, preclinical studies suggest that thyromimetic drugs, by targeting selected receptors, might be useful in the treatment of obesity and dyslipidemia.

“…This difference was related to the amount of lean body mass rather than to body weight by itself (59). After weight loss, a reduction in thyroid volume was also observed (60).…”

Section: Thyroid Function and Structure In Obese Subjectsmentioning

confidence: 92%

Section: Thyroid Function and Structure In Obese Subjectsmentioning

confidence: 99%

MECHANISMS IN ENDOCRINOLOGY: The crosstalk between thyroid gland and adipose tissue: signal integration in health and disease

Santini

Marzullo

Rotondi

et al. 2014

202

185

“…How these affect thyroid volume is unclear, but thyroid volume for BSA can be expected to differ between populations. A recent report has suggested that, in adults, thyroid size is determined largely by lean body mass (22). Whether this is also true in growing children remains to be established.…”

Section: Discussionmentioning

confidence: 99%

Local versus WHO/International Council for Control of Iodine Deficiency Disorders-recommended thyroid volume reference in the assessment of iodine deficiency disorders

Foo

Zulfiqar

Nafikudin

et al. 1999

Objective: Iodine deficiency endemia is defined by the goitre prevalence and the median urinary iodine concentration in a population. Lack of local thyroid volume reference data may bring many health workers to use the European-based WHO/International Council for Control of Iodine Deficiency Disorders (ICCIDD)-recommended reference for the assessment of goitre prevalence in children in different developing countries. The present study was conducted in non-iodine-deficient areas in Malaysia to obtain local children's normative thyroid volume reference data, and to compare their usefulness with those of the WHO/ICCIDD-recommended reference for the assessment of iodine-deficiency disorders (IDD) in Malaysia. Design and methods: Cross-sectional thyroid ultrasonographic data of 7410 school children (4004 boys, 3406 girls), aged 7-10 years, from non-iodine-deficient areas (urban and rural) in Peninsular Malaysia were collected. Age/sex-and body surface area/sex-specific upper limits (97th percentile) of normal thyroid volume were derived. Thyroid ultrasonographic data of similar-age children from schools located in a mildly iodine-deficient area, a severely iodine-deficient area, and a non-iodine-deficient area were also collected; spot urines were obtained from these children for iodine determination. Results: The goitre prevalences obtained using the local reference were consistent with the median urinary iodine concentrations in indicating the severity of IDD in the areas studied. In contrast, the results obtained using the WHO/ICCIDD-recommended reference showed lack of congruency with the median urinary iodine concentrations, and grossly underestimated the problem. The local sex-specific reference values at different ages and body surface areas are not a constant proportion of the WHO/ ICCIDD-recommended reference. A further limitation of the WHO/ICCIDD-recommended reference is the lack of normative values for children with small body surface areas (< 0.8 m 2 ) commonly found in the developing countries. Conclusion:The observations favour the use of a local reference in the screening of children for thyroid enlargement.

“…A recent study from our group questioned whether an elevated serum TSH alone provides sufficient evidence for a diagnosis of subclinical hypothyroidism in patients with morbid obesity (19). Little has been reported on the morphology of the thyroid gland in adults with morbid obesity (20,21). A recent study, performed in obese children, showed for the first time that obesity is associated with structural changes in thyroid morphology, as assessed by US, which are unrelated to thyroid autoimmunity (22).…”

Section: Introductionmentioning

confidence: 99%

A hypoechoic pattern of the thyroid at ultrasound does not indicate autoimmune thyroid diseases in patients with morbid obesity

Rotondi¹,

Cappelli²,

Leporati³

et al. 2010

Objective: Thyroid ultrasound (US) scan is a valuable tool for diagnosing thyroid diseases. In autoimmune thyroid disease (AITD), an hypoechoic pattern of the thyroid at US is related to circulating thyroid antibodies (Abs). The aim of this study was to evaluate the diagnostic accuracy of thyroid US for the detection of AITD in patients with morbid obesity. Design: Thyroid US scans showing an hypoechoic pattern of the thyroid were collected from 105 morbid obese patients (body mass index (BMI) O40 kg/m 2 ) and 105 non-obese patients (BMI%30 kg/m 2 ). Results: A thyroid hypoechoic pattern at US was consistent with clinical/biochemical features of AITD in 90/105 (85.7%) non-obese patients and in 22/105 (20.9%) morbid-obese patients (P!0.0001). By performing a complete thyroid work-up, including clinical examination, thyroid morphology, serum hormones, and auto-Ab measurements, the discrepancy between the US pattern and the results of the thyroid Ab tests was justified in 6/15 non-obese patients, and only in 1/83 morbid obese patients. Thus, an unexplained hypoechoic pattern of the thyroid at US, defined as negative tests for thyroid Ab and absence of justifying thyroid disturbances, was found in 2/105 (1.9%) non-obese patients and in 68/105 (64.8%) morbid obese patients (P!0.0001). Conclusions: Our results suggest that i) morbid obesity may affect thyroid morphology, and ii) an hypoechoic pattern of the thyroid at US, a well-established parameter for diagnosing AITD, has a poor diagnostic accuracy when patients with morbid obesity are taken into account.