Medicine (RMH) - Theses
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ItemHLA genetics of autoimmune Graves’ disease and the effects of lifestyle factors on the prevalence of Vitamin D deficiency in Vietnamese living in Melbourne( 2011)Background: There has been an increasingly high attendance rate of Vietnamese Graves’ disease (GD) patients at Western Hospital and local clinics in Melbourne. This proposes interplay between genetic and environmental factors, causing increased susceptibility to GD, which could be specific to Vietnamese. Evidence of HLA genetic susceptibility was established in Asian and Caucasian populations worldwide, but it is not defined in Vietnamese because HLA studies have not been carried out on this ethnic group. A possible environmental factor in GD is Vitamin D deficiency, which was found to be highly prevalent in the Vietnamese population of our previous study in 2008. Aims: This study aims to investigate HLA genetic factors associated with GD in Vietnamese and lifestyle factors associated with the prevalence of Vitamin D deficiency in Vietnamese living in Melbourne. Methods: There were 201 Vietnamese participants from recruitment, including 61 GD patients and 140 control participants. Prior to participation, all participants were subjected to a physical examination, where their medical and family history was obtained. Following the process of providing written consent for participation, all participants were asked to complete a Medical Questionnaire, Food Frequency Questionnaire and Sun Exposure Questionnaire, and have their height and weight measured for BMI calculation. Serology samples were collected from participants at the end of participation for HLA genotyping, and tested using Vitamin D assays and TRAb assays. Results: Associations were found between GD and two HLA-DRB1 alleles in Vietnamese. DR7 has a protective effect against GD in controls (OR 0.204, 95% CI 0.044-0.946, p-value 0.042) and DR9 has a predisposal effect to GD in cases (OR 2.247, 95% CI 1.156-4.366, p-value 0.017). There was no evidence of association between Vitamin D deficiency (<75 nmol/L) and GD. However, Vitamin D deficiency and insufficiency was determined to be as high as 85.6% (172 out of 201) in Vietnamese living in Melbourne. Mean serum 25(OH)D level in cases was 53.49 nmol/L (SD 20.73) and controls was 50.46 nmol/L (SD 23.60). Mean daily total Vitamin D intake per participant excluding supplements (381.174 IU) is lower than Recommended Daily Intake (400 IU/day) for adults and adolescents. Mean daily total calcium intake per participant (429.123 mg) is much lower than Recommended Daily Intake (1,000 mg/day) for adult men and women. Significant associations exist between Vitamin D deficiency and age, and two lifestyle factors including sun exposure and sun avoidance. Conclusion: For the first time, HLA genetic profile in association with GD was reported in a Vietnamese population, adding to the existing knowledge of HLA genetics in Asians. Better understanding of the genetic background for GD could potentially lead to improved diagnosis and treatment methods, as well as being useful for developing primary prevention strategies in GD. This research study also confirmed the high prevalence of Vitamin D deficiency in Vietnamese living in Melbourne and identified associated lifestyle factors for this condition.