Elevated parathyroid hormone predicts high asymmetric dimethylarginine (ADMA) concentrations in obese diabetic patients

The “classical” effects of vitamin D and parathyroid hormone (PTH) are to regulate calcium and mineral homeostasis. Recently, it is increasingly suggested that vitamin D is important in cardiovascular homeostasis, and conversely, that vitamin D deficiency may represent a risk factor for the development of coronary disease. Low vitamin D levels leads to reduced intestinal absorption of calcium, and thus triggers the secretion of PTH from parathyroid glands, which in turns are responsible for increasing calcium levels. In addition to its effects in regulating calcium and mineral homeostasis, elevated levels of PTH with either primary hyperparathyroidism or secondary hyperparathyroidism, have also been associated with increased adverse cardiovascular effects. Patients with chronic elevation of PTH levels are at increased risk of insulin resistance, dyslipidemia, heart failure, hypertension, cardiac hypertrophy, and myocardial infarction. Impaired vascular endothelial function has been suggested as a possible mechanism to explain the nexus between vitamin D deficiency and increased adverse cardiovascular outcomes. In addition, elevated PTH is also found associated with increased arterial stiffness and impaired endothelial function, improved after lowering of PTH with parathyroidectomy. Previously, we have shown that in an ageing population, low vitamin D levels are associated with elevated plasma concentrations of asymmetric dimethylarginine (ADMA). Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of endothelial nitric oxide synthase (eNOS), has been shown to be a critical circulating biomarker of endothelial function, and adverse cardiovascular outcomes. However, we did not assess the relationship between ADMA and PTH. Given, the high prevalence of low vitamin D and high parathyroid hormone (PTH) levels in obese diabetic patients, we sought to examine in this study, whether the relationship between ADMA and vitamin D is independent of PTH levels in obese diabetic