Endocrine Abstracts

Introduction: Serum 25(OH) vitamin D levels are shown to be significantly lower and associated with lower remission rates in Graves disease. In this study we aimed to investigate the impact of baseline vitamin D levels on thyroid volume in patients with new-onset Graves disease.

Materials and methods: This is a monocenter cross sectional study with a total of 61 new-onset Graves disease patients (n:61, F: 40, M:21) who were divided into two groups according to baseline serum vitamin D levels, as Group-1 (D vit <20; n:42) and Group-2 (D vit ≥20; n:19). Plasma fT4, fT3, TRAb, TPOAb and PTH levels were analysed and thyroid volume (ml), isthmus thickness (mm) were measured by the same physician with thyroid ultrasonography at the time of diagnosis for each patient. The results were compared between the two groups. Categorical variables were processed with the chi-square test. Pearson and spearman correlation analysis were performed for normally and non-normally distributed data, respectively.

Results: There was an inverse correlation between baseline serum vitamin D levels and thyroid volume, TRAb, fT3 and PTH levels (P=0.02, r=−0.31; P=0.005, r=−0.36; P=0.04, r=−0.26; P=0.02, r=−0.32; respectively). Thyroid volume was also correlated with serum fT4, fT3, TRAb and TPOAb (P=0.001, r=0.426; P=0.001, r=0.50; P=0.04, r=0.26; P=0.001, r=0.42; respectively). Low vitamin D and high TgAb levels were independently associated with thyroid volume in logistic regression analysis (P=0.03, OR:18.7, CI 95% 1.34–260.91 and P=0.04, OR: 16.6, CI 95% 1.07–255.64; respectively).

Conclusion: Baseline serum vitamin D levels are inversely related with thyroid volumes, fT3 and TRAb levels in new-onset Graves disease. In addition to several advantages, optimization of vitamin D levels would also be beneficial in the surveillance of these patients. However larger scale studies are required in order to make further suggestions.