Endocrine Abstracts

Background: Risk of cardiovascular disease (CVD) and mortality is increased in Graves’ disease (GD) even years after initial diagnosis and treatment. The mechanisms are incompletely understood. Vitamin D insufficiency is associated with an increased risk of CVD and has been reported to occur frequently in GD. Pulse wave velocity (PWV) and blood pressure (BP) are important predictors of CVD. We performed a clinical trial, testing whether vitamin D supplementation affects PWV and BP in GD.

Methods: Using a double-blinded design, 86 hyperthyroid patients with a first time diagnosis of GD were randomized to vitamin D 70 mcg/day or matching placebo as add on to standard antithyroid medication (ATD). At baseline and after three and nine months of intervention, we measured PWV, augmentation index (Aix), brachial and central BP in both office (SphygmoCor Xcel) and 24h setting (Arteriograph). Differences in change between groups were analysed using linear mixed modelling. In subanalysis, interaction between intervention and presence of baseline vitamin D insufficiency (25(OH)D<50 nmol/L) was tested. (The DAGMAR study clinicaltrials.gov ID NCT02384668).

Results: Nine months of vitamin D supplementation did not affect PWV or Aix. Office central systolic BP declined by −3.9 (95%CI:−7.5;−0.3) mmHg and office brachial mean arterial BP declined by −3.3 (95%CI:−6.5;−0.3) mmHg in response to vitamin D supplementation. However, supplementation had no effect on 24h BPs. Compared to patients with a replete vitamin D status, PWV decreased significantly by −1.2 (95%CI:−2.3;−0.1) m/s in the group of patients with 25(OH)D levels <50 nmol/l (n=28). The reduction of PWV was partly mediated by a decrease in central systolic BP. There were non-significant differences in baseline characteristics in this subanalysis, and the observed response might reflect regression towards the mean.

Conclusion.: Overall, nine months on vitamin D supplementation as add on the standard ATD did not affect PWV and BP in patients newly diagnosed with GD. Whether vitamin D supplementation is of benefit to PWV in GD patients with vitamin D insufficiency needs further investigation.