Endocrine Abstracts

Introduction: The role of vitamin D in GD is poorly understood. The aim was to compare vitamin D levels in newly diagnosed patients with GD with the general population and to correlate vitamin D levels at diagnosis with laboratory and clinical parameters in GD. Moreover, we examined genetic variation in genes involved in the vitamin D metabolism and their association with GD.

Material and methods: Levels of vitamin D were compared in 292 patients with newly diagnosed GD and 2305 controls. Single nucleotide polymorphisms (SNPs) in the vitamin D receptor (VDR), vitamin D binding protein (DBP) and 1-alpha-hydroxylase (CYP27B1) were examined for association with GD and/or Graves’ ophthalmopathy (GO) in 708 patients and 1178 controls.

Results: Patients with GD had significantly lower levels of vitamin D compared to general population (55.0±23.2 vs 87.2±27.6 nmol/l, P<0.001). In patients with GD (n=219), there was no association between the levels of vitamin D and the levels of free thyroxine (fT4), free triiodothyronine (fT4), thyrotropin receptor antibodies (TRAb), GO at diagnosis, or relapse after terminating treatment with anti-thyroid drugs. Two SNPs in VDR were associated with GD, rs10735810 (OR 1.36, 95% CI 1.02–1.36, P=0.02) and rs1544410 (OR 1.47, 95% CI 1.03–1.47, P=0.02). However, there was no difference in mean vitamin D levels between genotypes in either rs10735810 (AA 55.9 nmol/l, AG 56.1 nmol/l, GG 54.1 nmol/l, P=n.s.) or rs1544410 (AA 56.6 nmol/l, AG 57.5 nmol/l, GG 54.8 nmol/l, P=n.s.).

Conclusion: Patients with GD have lower vitamin D levels compared with general population; however, the levels of vitamin D do not affect the laboratory or clinical parameters of the disease. SNPs in the VDR influence the risk of GD through mechanisms other than reducing the vitamin D levels.