Graves disease: Patients with hyperthyroid status have a higher risk of developing type 2 diabetes

RIBERI, MI; GASTÓN, M.S.; CASTILLO, AL

Philadelphia

Encuentro; 2016 AACC Annual Meeting & Clinical Laboratory Expo; 2016

Introduction. Graves? disease (GD) is a multi-systemic autoimmune disorder caused by thyroid stimulating antibodies that bind to and activate the thyroid stimulating hormone (TSH) receptor on thyroid cells (TRAbs). Common findings are low serum concentration of TSH, positive TRAbs, and high concentrations of anti-thyroid peroxidase antibodies (ATPO). In insulin-dependent diabetics, hyperthyroidism may aggravate glucose intolerance by multiple mechanisms, decreasing responsiveness to insulin. An association between type 1 diabetes mellitus (DM) and autoimmune reaction to thyroid antigens, including anti-thyroid antibodies (ATPO) in pediatric patients with positive TRAbs, was recently reported. The objective of this study is to investigate the association between thyroid status, serum TSH levels, positive TRAbs and ATPO, and the potential risk to develop type 2 DM based on insulin levels in adults.Materials and methods. The study was conducted in 64 patients between May 2014 and October 2015. The mean subject age was 47 ± 18 years old and the male/female ratio was 11 (17.7% male): 51(82.3%female). Pregnant women and patients under 25 years of age were excluded. We measured TRAbs, ATPO, TSH, and insulin concentrations in euthyroids (TSH = 1.10 to 9.00 µU/mL) and hyperthyroids (TSH between 0.01 to 0.44 µU/mL). TRAbs were measured by second generation thyrotropin-binding inhibitor immunoglobulin (TBII) assay (DiaMetra, Italy). The cut-off for positive TRAbs was 1.50 UI/L. ATPO, TSH and insulin concentrations were determined by chemiluminescent microparticle immunoassay (CMIA) using a Advia Centaur (Siemens, USA). The cut off for positive ATPO was > 37 UI/mL, reference interval for TSH was 0.4 to 4.4 µU/mL and for insulin was 5 to 20 µU/mL. Data obtained for all measurements of TRAbs, ATPO, TSH and insulin in both groups was analyzed using the Student?s t-test. A p value < 0.05 represented a significant difference. Data was expressed as mean ± standard error of the mean (SEM).Results. As expected, TSH serum concentrations were significantly decreased in hyperthyroid patients (0.13 ± 0.03) compared with euthyroid patients (3.31 ± 0.48) (t=12.79; p < 0.05). We observed a significant increase in TRAbs levels in hyperthyroid patients (7.67 ± 1.91) compared with euthyroid patients (2.23 ± 0.40) (t=2.07; p < 0.05). In addition, we reported a significant enhacement on ATPO levels in hyperthyroid patients (650.8 ± 84.82) versus euthyroid patients (296.2 ± 85.30) (t=3.03; p < 0.05). Similarly, higher insulin levels were observed in hyperthyroid patients (15.35 ± 1.94) versus euthyroid patients (9.94 ± 1.43) (t=2.51; p < 0.05). Conclusions. Based on the results of the present study we conclude that thyroid autoimmunity is associated with female gender, the presence of anti-thyroid and TSH receptor antibodies, and low levels of TSH. Importantly, higher mean insulin concentrations were observed in hyperthyroid patients. The presence of TRAbs and high insulin concentrations in patients with TSH between 0.01-0.44 µU/mL and positive ATPO, may indicate a higher risk of developing type 2 Diabetes Mellitus in adults. We recommend evaluation of TRAbs and insulin levels in at-risk populations