The Influence Of Thyroid Function On Obesity And Its Related Metabolic Abnormalities

Chapter 1:The changes of thyroid function in obesityObjective:To investigate the proportion of different thyroid dysfunctions in individuals with obesity in our health examinations,including clinical hyperthyroidism,clinical hypothyroidism,subclinical hyperthyroidism and subclinical hypothyroidism,and the influence of thyroid dysfuctions on hyperglycemia,dyslipidemia,hypertension,and metabolic syndrome(MS).Methods:1370 subjects were evaluated for routine health examination in our hospital from November 2013 to February 2014 without history and family history of thyroid diseases.According to International Diabetes Federation(IDF)and American Heart Association/National Heart Lung and Blood Institute(AHA/NHBLI)diagnostic criteria for MS,we diagnosed obesity when the waist is higher than 85cm in male and 80cm in female.587 individuals were diagnosed with obesity and 783 without.Blood samples were tested in 278 individuals,including 38 MHO,30 obesity with dyslipidemia,28 obesity with glucose abnormalities,126 obesity with MS and 56 normal weight and metabolically healthy(NWMH)cases.Parameters were evaluated including height,weight,waist circumference,hip circumference and blood pressure by 3 fixed doctors.Serum free thyroxine(FT4),free triiodothyronine(FT3),thyroid stimulating hormone(TSH),triglyceride(TG),total cholesterol(TC),high density lipoprotein(HDL),low density lipoprotein(LDL),serum alanine aminotransferase(ALT),serum creatinine(CR),blood urea nitrogen(BUN),blood uric acid(UA),peripheral white blood cell count(WBCC)were detected in 278 individuals.Calculate the proportion of different thyroid dysfunctions which turned out to be clinical hyperthyroidism,clinical hypothyroidism,subclinical hyperthyroidism and subclinical hypothyroidism,and compared the risk of hyperglycemia,dyslipidemia,hypertension and MS in obese ones with and without thyroid dysfunction.Results:1.In 222 individuals who were obese,33(14.9%)were found abnormal thyroid function.1(0.5%)can be referred to as clinical hyperthyroidism,25(11.3%)as subclinical hypothyroidism,2(0.9%)as mild clinical hyperthyroidism and 1(0.5%)as subclinical hyperthyroidism.Other conditions also existed including 1 with elevated FT4,2 with decreased FT3 and 1 with decreased FT4.In 56 individuals with normal weight and metabolically healthy,5(8.9%)cases were diagnosed thyroid dysfunction.Among them,3(5.4%)were subclinical hypothyroidism,1 with decreased FT4 and 1 with elevated FT3.2.Compared with obese and euthyroid ones,obese individuals with subclinical hypothyroidism owned higher age,BMI and BUN.3.compared with obese and euthyroid ones,obese individuals with subclinical hypothyroidism has higher risk of MS(64.0%vs 57.1%,P<0.05).Conclusions:1.Among obese people of routine health examination in a 3-grade hospital in Hunan,14.9%had abnormal thyroid function,11.3%had subclinical hypothyroidism.2.Obese individuals are more likely to result in MS when they have thyroid abnormality.Chapter 2:The changes of serum thyroid hormones in different subtypes of obesityObjective:To investigate the changes of serum thyroid hormones in different subtypes of obesity.Methods:The subjects and methods of data collection were the same as chapter1.According to different metabolic status,we divided obese individuals into three subtypes:(1)Metabolic healthy obese(MHO):obese with normal profile of blood glucose,blood lipids and blood pressure.(2)Obese with one metabolic defect:obese with one of the abnormalities including elevated blood glucose,abnormal lipid profile or increase blood pressure.(3)Obese with MS.We selected individuals who were normal both on weight and metabolic status as normal controls.Compared the levels of thyroid hormones in MHO,obese with one metabolic defect,MS with normal controls,and try to explore changes of levels of serum thyroid hormones in different subtypes of obesity.Results:1.In three different subtypes of obesity,the levels of serum FT3 and FT4 were significantly decreased compared with normal controls(P<0.05).2.Compared with MHO,obese individuals with abnormal blood glucose and those accompanied by MS owned significantly decreased levels of FT3(P<0.05).Conclusions:The levels of serum FT3 and FT4 were significantly decreased in three different subtypes of obesity from MHO to obese with one metabolic defect and obese with MS,while FT3 was decreased further when metabolic disorders occurred.Chapter 3:Relationship between changes of serum thyroid hormone in normal range and obesity related disordersObjective:To investigate the proportion of obesity,hyperglycemia,dyslipidemia,hypertension and MS in different quarters of levels of serum thyroid hormones in normal range,calculate the fluctuation of serum thyroid hormones from the midline in different subtypes of obesity,explore the relationship between the changes of serum thyroid hormones in normal range and obesity related disorders.Methods:Subjects were the same as chapter 1.In 278 cases with tested serum thyroid functions,240 euthyroid individuals were enrolled in the study.Compare clinical,biochemical features and the risk of obesity related metabolic abnormalities between different quartiles of serum FT3,FT4 and TSH in normal range.Mean values of serum FT3,FT4 and TSH of 240 euthyroid individuals within normal range were5.16 pmol/L,17.10 pmol/L and 2.16 mlU/L respectively.Fluctuation of serum FT3,FT4 and TSH was calculated as original value minus mean value.Compare the changes of serum thyroid hormones between MHO,obese with dyslipidemia,obese with abnormal blood glucose,MS and those with normal weight and metabolic healthy.Results:1.In four quartiles of serum FT3 levels from the lowest group A1 to the highest group A4,group A1,A2 and A3 had higher percentage of MS compared with group A4(72.9%,66.7%,31.1%vs 10.0%,P<0.05).2.In four quartiles of serum FT4 levels from the lowest group B1 to the highest group B4,group B1,B2 had higher percentage of MS compared with group B4(50.8%,57.4%vs 28.3%,P<0.05).3.In four quartiles of serum TSH levels from the lowest group PI to the highest group P4,group P1 had higher percentage of MS(60%vs 35%)and lower percentage of MHO(5.0%vs 21.7%)compared with group P4.4.After calculated the fluctuation value of serum FT3,FT4 and TSH,we found that serum FT3 levels decreased in MHO group,obese group with abnormal glucose,obese group with MS,FT4 levels decreased in MHO and obese group with MS,TSH levels increased in MHO and decreased in obese group with MS compared with normal controls(P<0.05).we found that FT3 levels decreased in obese group with abnormal glucose,obese group with MS,TSH levels decreased in obese group with MS compared with MHO group(P<0.05).Conclusion:1.When serum FT3,FT4 and TSH values were in the highest quartile of normal range,the metabolic status of obese individuals tend to be normal,which is called MHO.When FT3,FT4 and TSH values were in the lowest quartile,obese individuals were often accompanied by metabolic disorders and MS.2.Increased serum TSH levels within normal range can help MHO maintain healthy metabolic state.