A Review of Current Clinical Concepts in the Pathophysiology, Etiology, Diagnosis, and Management of Hypercalcemia.

Calcium is the most abundant extracellular cation in the body, and it is responsible for structural and enzymatic functions. Calcium homeostasis is regulated by 3 factors: calcitonin, vitamin D, and parathyroid hormone (PTH). Hypercalcemia is defined by a serum calcium concentration >10.5 mg/dL, and it is classified into mild, moderate, and severe, depending on calcium values. Most cases are caused by primary hyperparathyroidism and malignancies. Various mechanisms are involved in the pathophysiology of hypercalcemia, such as excessive PTH production, production of parathyroid hormone-related protein (PTHrp), bone metastasis, extrarenal activation of vitamin D, and ectopic PTH secretion. The initial approach is similar in most cases, but a definitive treatment depends on etiology, that is why etiological investigation is mandatory in all cases. The majority of patients are asymptomatic and diagnosed during routine exams; only a small percentage of patients present with severe manifestations which can affect neurological, muscular, gastrointestinal, renal, and cardiovascular systems. Clinical manifestations are related to calcium levels, with higher values leading to more pronounced symptoms. Critically ill patients should receive treatment as soon as diagnosis is made. Initial treatment involves vigorous intravenous hydration and drugs to reduce bone resorption such as bisphosphonates and, more recently, denosumab, in refractory cases; also, corticosteroids and calcitonin can be used in specific cases. This review aims to provide a clinical update on current concepts of the pathophysiology of calcium homeostasis, epidemiology, screening, clinical presentation, diagnosis, and management of hypercalcemia.

Vitamin D induces increased systolic arterial pressure via vascular reactivity and mechanical properties.

BACKGROUND/AIMS: The aim of this study was to evaluate whether supplementation of high doses of cholecalciferol for two months in normotensive rats results in increased systolic arterial pressure and which are the mechanisms involved. Specifically, this study assesses the potential effect on cardiac output as well as the changes in aortic structure and functional properties. METHODS: Male Wistar rats were divided into three groups: 1) Control group (C, n = 20), with no supplementation of vitamin D, 2) VD3 (n = 19), supplemented with 3,000 IU vitamin D/kg of chow; 3) VD10 (n = 21), supplemented with 10,000 IU vitamin D/kg of chow. After two months, echocardiographic analyses, measurements of systolic arterial pressure (SAP), vascular reactivity, reactive oxygen species (ROS) generation, mechanical properties, histological analysis and metalloproteinase-2 and -9 activity were performed. RESULTS: SAP was higher in VD3 and VD10 than in C rats (p = 0.001). Echocardiographic variables were not different among groups. Responses to phenylephrine in endothelium-denuded aortas was higher in VD3 compared to the C group (p = 0.041). Vascular relaxation induced by acetylcholine (p = 0.023) and sodium nitroprusside (p = 0.005) was impaired in both supplemented groups compared to the C group and apocynin treatment reversed impaired vasodilation. Collagen volume fraction (<0.001) and MMP-2 activity (p = 0.025) was higher in VD10 group compared to the VD3 group. Elastin volume fraction was lower in VD10 than in C and yield point was lower in VD3 than in C. CONCLUSION: Our findings support the view that vitamin D supplementation increases arterial pressure in normotensive rats and this is associated with structural and functional vascular changes, modulated by NADPH oxidase, nitric oxide, and extracellular matrix components.