J Huazhong Univ Sci Technol［Med Sci］ DOI 10.1007/s11596-012-0008-8 32(1):47-52,2012 J Huazhong Univ Sci Technol［Med Sci］ 32(1):2012
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Relationship between Serum TSH Level with Obesity and NAFLD in Euthyroid Subjects* Jiaoyue ZHANG (张皎月)†, Hui SUN (孙 晖)†, Lulu CHEN (陈璐璐)#, Juan ZHENG (郑 涓), Xiang Hu (胡 祥), Suxing WANG (王素星), Ting CHEN (陈 婷) Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China © Huazhong University of Science and Technology and Springer-Verlag Berlin Heidelberg 2012
Summary: To explore the relationship between serum thyroid stimulating hormone (TSH) level and obesity and nonalcoholic fatty liver disease (NAFLD) in euthyroid subjects, 1322 subjects were subjected to a questionnaire survey and physical examination. Fasting blood samples were collected to test serum TSH, plasma glucose and lipids. Fatty liver was diagnosed by type B ultrasonography. The relationship between serum TSH level and body mass index (BMI), percentage of body fat and NAFLD was analyzed. The results showed that serum TSH level was significantly higher in females than in males at the same group, and it was significantly higher in overweight group than in control group. Levels of body weight, BMI, waist circumference and percentage of body fat were increased in TSH >2.5 group compared to TSH ≤2.5 group in women. However, plasma lipids showed no significant differences. In males all the parameters showed no significant differences between two groups. Serum TSH was significantly correlated with body weight, BMI, waist circumference and percentage of body fat after adjustment for age in females. Multiple linear regression analysis revealed that percentage of body fat and BMI contributed significantly to the variance of TSH. Serum TSH level was significantly higher in nonalcoholic fatty liver group than in normal group in females. Multiple logistic regression analysis showed that TSH level was not the independent risk factor of NAFLD. Taken together the data suggest that serum TSH in normal range is significantly correlated with BMI and percentage of body fat in females. And the change of TSH level would not influence the prevalence of NAFLD. Key words: thyroid stimulating hormone; obesity; lipid; thyroid function; nonalcoholic fatty liver disease
Thyroid hormones play an important role in thermogenesis and influence all major metabolic pathways such as protein, carbohydrate and lipid metabolism[1, 2]. Abnormal secretion of thyroid hormones would cause the change of weight, lipid, blood pressure and sugar. Severe hypothyroidism is usually associated with an increased serum concentration of atherogenic lipoproteins[3, 4]. Thyrotoxicosis is always companied with weight loss and malnutrition[5]. However, the effects of thyroid hormones in normal range on the fat storage and metabolism are relatively less studied and paradoxical. Ambrosi et al[6] reported in 581 obese patients, thyroid stimulating hormone (TSH) levels were progressively increased according to the severity of obesity and were positively correlated with body mass index (BMI), waist circumJiaoyue ZHANG, E-mail:
[email protected]; Hui SUN, E-mail:
[email protected] † The authors contributed equally to this work. # Corresponding author, E-mail:
[email protected] * The project was supported by grants from the epidemiological study on the thyroid disease in ten-city communities in China, and Wuhan Science and Technology Research Program of China (No. 201161038340-02).
ference and insulin resistance. Yet the opposite suggestion had also been put forward that TSH was not correlated with BMI in euthyroid females[7]. In the present study we sought to evaluate thyroid function within the normal range and to determine its possible relationship with BMI, percentage of body fat (PBF), plasma lipids and nonalcoholic fatty liver disease (NAFLD) in euthyroid subjects. TSH has been widely accepted as the primary test and “gold standard” for diagnosing and managing most thyroid conditions, so it was selected and measured as the sole indicator of thyroid function. 1 MATERIALS AND METHODS 1.1 Subjects A Wansong urban community-based sample of 1500 adult inhabitants in Wuhan of Hubei province was enrolled in the survey between January and April in 2010. The age composition drawn in the survey was apportioned according to the recent nationwide urban population census. And a sex ratio was controlled in 1―1.5:1 (female:male). Of these, 178 adults were excluded for any of the following reasons: history of thyroid disease, abnormal thyroid hormone levels (including subclinical
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J Huazhong Univ Sci Technol［Med Sci］ 32(1):2012
hyperthyroidism and hypothyroidism), treatment history of antithyroid drugs, dopamine or corticosteroids, pregnancy or post partum within last year, severe hepatic and renal dysfunction. 1322 subjects were considered eligible for this study. The study was reviewed and approved by the local ethics committee and informed consent was obtained from all the subjects. 1.2 Questionnaire Survey Survey contents included: name, sex, ethnicity, age, home address, telephone number, occupation, education background, monthly income, childbearing history, smoking history, family history, medical history including thyroid diseases, and medication status. 1.3 Anthropometrical Measurements Body weight (kg) and height (m) were measured while subjects wore light clothing and no shoes. BMI was calculated as weight divided by squared height (kg/m2). Strictly, the waist circumference was measured at a level midway between the lowest rib and the iliac crest, and the hip circumference at the level of the great trochanters, with the legs close together[8]. Waist-to-hip ratio (WHR) was calculated as the ratio of the circumference of the waist to that of the hips. Blood pressure (mmHg) was measured twice in the upper arm after a 10-min period of rest and taken an average. The PBF was measured with the bioelectrical impedance analysis method using TANITA TBF-300A. 1.4 Laboratory Methods Fasting blood samples were obtained from a subcutaneous vein in the forearm, centrifuged at room temperature and the plasma or serum separated and stored at –20°C until analysis. Plasma lipid levels including cholesterol, triglyceride and LDL, and glucose levels (mmol/L) were measured by an autoanalyser (AU5421, Olympus, Hong Kong, China). Serum levels of TSH (mIU/mL, reference range 0.71―6.25) were determined by using super-sensitive chemiluminescence immunoassay (IMMULITE, Diagnostic Products Corporation,
USA). An intra-assay coefficient of variation (CV) was less than 8% and an inter-assay CV less than 10% in all above parameters. 1.5 Liver B-ultrasound Examination A liver examination by high resolution ultrasound (SSD prosound α10 color Doppler ultrasonograph, Aloka, Japan) was taken for the diagnosis of fatty liver for analysis. 1.6 Statistical Analyses All statistical analyses were performed using SPSS 13.0 software, and a two-tailed P-value
