The effect of vitamin D3 supplementation on markers of cardiovascular health in hyperparathyroid, vitamin D insufficient women: a randomized placebo-controlled trial

Purpose Emerging data supports an association between parathyroid hormone (PTH) and aldosterone. It has been speculated, that potential adverse cardiovascular effects of vitamin D insufficiency may partly be caused by the development of secondary hyperparathyroidism with increased activity of the renin-angiotensin-aldosterone system (RAAS). We aimed to investigate the effect of normalizing vitamin D status and/or reducing PTH levels on RAAS activity and other markers of cardiovascular health. Methods In a double-blinded study during wintertime, we randomized 81 healthy postmenopausal women with secondary hyperparathyroidism (PTH > 6.9 pmol/l) and 25-hydroxy-vitamin D (25(OH)D) levels < 50 nmol/l to 12 weeks of treatment with vitamin D3 70 µg/day (2800 IU/day) or identical placebo. Markers of cardiovascular health were defined as changes in the plasma RAAS, glycated hemoglobin, lipids, and lipoproteins, blood pressure, vascular stiffness, heart rate, and cardiac conductivity. Results Compared to placebo, vitamin D3 treatment significantly increased plasma levels of 25(OH)D and 1,25(OH) 2 D by 230% (95% CI: 189–272%) and 58% (190–271%), respectively. Vitamin D3 treatment reduced PTH by 17% (11–23%), but did not reduce RAAS activity. Compared to placebo, vitamin D3 treatment increased plasma levels of high-density lipoproteins (HDL) by 4.6% (0.12–9.12%), but did not affect other measured indices. Conclusions Vitamin D3 supplementation normalized vitamin D levels and reduced PTH. The supplement increased levels of HDL, but had no effects on RAAS activity or other indices of cardiovascular health.