DIO2 enzyme gene polymorphism relation with the TRH stimulation test and obesity in euthyroid patients

The relation between obesity and the thyroid hormones are conflicting. But the diminished TH effect could be a reason for the obesity. This study was made to determine the role of the DIO2 gene polymorphism in the obesity.We enrolled 96 obese euthyroid patients and 90 healthy control subjects. DIO2 gene polymorphism and basal TSH levels were measured and compared in both groups. Also TRH stimulus test was applied to the patients. Thirty minute TSH response of this test was evaluated that whether there is a relation with DIO2 gene polymorphism, allele frequency and basal TSH levels or not. Insulin resistance parameter HOMA-IR and DIO2 gene polymorphism relation is also investigated.Genetic polymorphism (p=0.396) and allele frequency (p=0.276) were similar in the patient and control groups. Patients were divided into group1 (GG) and group 2 (GA+AA) according to DIO2 genotype. There were no BMI (p=0.835), basal TSH (p=0.881), 30th minute TSH levels in TRH stimulus test (p=0.593) and HOMA-IR (p=0.886) differences in both groups. Patients were grouped as depressed response, normal response and exaggerated response in the TRH stimulus test. There were no differences of genetic polymorphism (p=0.100), BMI (p=0.977), HOMA-IR (p=0.603) and body type (p=0.682) between three groups. Patients were classified as group 1 (TSH ? 2.5 uIU/mL) and group 2 (TSH> 2.5 uIU/mL). There were 4.7% exaggerated response patients in group 1 and 40% in group 2 (p=0.001). There were 49 AA (57.6%),25 AG (29.4%) 11 GG (12.9%) genotype patients in group 1. Interestingly there were 4 AA (36.4%),7 AG (63.6%) (p=0.059) genotype patients in group 2. Group 2 had no GG genotype. These groups were not different in terms of BMI (p=0.425) and HOMA-İR (p=0.557). Besides there was positive correlation between basal TSH levels and TRH stimulus test response (r= +0.49, p=0.000) in patients. There were no difference of the basal TSH levels (p=0.241) and TRH stimulus test response (p=0.442) between the A allele carrying group and other groupIn conclusion we didn't find any relation between DIO2 enzyme gene Ala92The polymorphism and TRH stimulus test response and obesity. On the other hand it may be interesting that in patients with basal TSH levels ?2.5 uIU/mL had more AG allele and no GG allele in the DIO2 enzyme genotype. Thyroid hormone deficiency can increase the obesity. So it would be helpful to make TRH stimulus test evaluation in patients with basal TSH levels between 2.5-4 uIU/mL.Key words: Obesity, DIO2 gene polymorphism, BMI, HOMA-İR, TRH, TSH.