Overweight and obesity in children and adolescents with chronic autoimmune thyroiditis

Causal association between obesity and hypothyroidism: a two-sample bidirectional Mendelian randomization study

Introduction

Previous observational studies have reported a positive correlation between obesity and susceptibility to hypothyroidism; however, there is limited evidence from alternative methodologies to establish a causal link.

Methods

We investigated the causal relationship between obesity and hypothyroidism using a two-sample bidirectional Mendelian randomization (MR) analysis. Single-nucleotide polymorphisms (SNPs) associated with obesity-related traits were extracted from a published genome-wide association study (GWAS) of European individuals. Summarized diagnostic data of hypothyroidism were obtained from the UK Biobank. Primary analyses were conducted using the inverse variance-weighted (IVW) method with a random-effects model as well as three complementary approaches. Sensitivity analyses were performed to ascertain the correlation between obesity and hypothyroidism.

Results

MR analyses of the IVW method and the analyses of hypothyroidism/myxedema indicated that body mass index (BMI) and waist circumference (WC) were significantly associated with higher odds and risk of hypothyroidism. Reverse MR analysis demonstrated that a genetic predisposition to hypothyroidism was associated with an increased risk of elevated BMI and WC, which was not observed between WC adjusted for BMI (WCadjBMI) and hypothyroidism.

Discussion

Our current study indicates that obesity is a risk factor for hypothyroidism, suggesting that individuals with higher BMI/WC have an increased risk of developing hypothyroidism and indicating the importance of weight loss in reducing the risk of hypothyroidism.

Overweight and obesity in children and adolescents with endocrine disorders

Obesity has become a serious medical condition where many factors can contribute to excess weight gain. The most common type of childhood obesity is simple obesity, which is due to gene-obesogenic environment interaction. Only a minority are due to pathological causes. Secondary causes of obesity, while less common, include these: genetic syndromes, drug-related obesity, as well as endocrine disorders (hypothyroidism, Cushing's syndrome, growth hormone deficiency, hypogonadism, pseudohypoparathyroidism type Ia, insulinoma, hypothalamic obesity and polycystic ovary syndrome). Given that some conditions may be treatable, physicians must be aware of obesity due to endocrinopathies and distinguish them from simple obesity, and treat them properly. Although rare among children, early detection of the endocrine cause of obesity leads to reduced morbidity and, in some cases, reduced mortality in these individuals. The aim of this review is to summarize the current findings on obesity-related endocrinopathies in children (illustrated by clinical examples), highlighting aspects of pathogenetic mechanisms, genetics, the clinical diagnosis, growth, body mass index and possible therapeutic approaches. Early detection and correction of endocrine obesity is of paramount importance for obese children who could benefit from timely diagnosis and an improved management of obesity as many disturbances related to obesity can be reversed at the early stage, if weight loss is achieved.