Vitamin D Toxicity and Clinical Consequences of Hypervitaminosis

Vitamin D is an essential fat-soluble vitamin that enters the human body with certain animal products, fortified foods, dietary supplements, and is also synthesized endogenously under the influence of solar radiation. It plays a critical role in regulating calcium-phosphorus metabolism and maintaining bone health, preventing the development of rickets and osteopenia. In recent years, there has been a growing body of evidence regarding its involvement in numerous metabolic processes and potential link to the risk of autoimmune diseases, cancer, cardiovascular disease, depression, dementia and infectious diseases. However, despite the widespread use and availability of vitamin D, including in the form of over-the-counter supplements, there is a risk of developing hypervitaminosis D, which, although rare, can have serious clinical consequences. Vitamin D toxicity is usually caused by excessive intake of high doses of the vitamin (intentional or accidental), prescription errors, or lack of proper monitoring of vitamin D levels during treatment of certain diseases (e.g., osteoporosis, renal osteodystrophy, malabsorption). Clinical manifestations of hypervitaminosis D are caused by hypercalcemia and can range from nonspecific symptoms (weakness, fatigue, anorexia, bone pain) to more serious neurological (confusion, apathy, ataxia), gastrointestinal (nausea, vomiting, constipation, pancreatitis), renal (polyuria, polydipsia, nephrolithiasis) and cardiac (arrhythmias) disorders. Treatment is mainly supportive and aimed at lowering calcium levels by discontinuing vitamin D and calcium intake, rehydration, and in severe cases, calcitonin, bisphosphonates, sometimes glucocorticoids, or hemodialysis.