Vitamin D toxicity Domina Petric MD Vitamin D

Vitamin D toxicity Domina Petric, MD

Vitamin D toxicity • Excessive intakes of vitamin D are associated with increases in circulating levels of 25 -OH-D 3. • The 25 -OH metabolite is believed to be the critical metabolite in vitamin D intoxication. • At high levels, it appears to compete successfully for intracellular receptors for 1, 25 -(OH)2 -D 3, thus inducing the responses normally produced by the latter metabolite. January 5, 2022 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. 2

Vitamin D toxicity • Hypervitaminosis D involves increased enteric absorption and bone resorption of calcium, producing hypercalcemia, with attendant decreases in serum PTH and glomerular filtration rate and, ultimately, loss of calcium homeostasis. • The mobilization of bone also results in increased serum concentrations of zinc from that reserve. January 5, 2022 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. 3

Signs of hypervitaminosis D Anorexia Gastrointestinal distress Nausea and vomiting Headache Weakness, lameness Polyuria, polydypsia Nervousness Hypercalcemia Calcinosis January 5, 2022 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. 4

Vitamin D toxicity • With chronically elevated serum calcium and phosphorus levels, the ultimate result is calcinosis. • Calcinosis is the deposition of calcium and phosphate in soft tissues, especially heart and kidney, but also the vascular and respiratory systems and all other tissues. January 5, 2022 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. 5

Calcinosis cutis Dermatologyadvisor. com January 5, 2022 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. 6

Vitamin D toxicity The risk of hypervitaminosis D is dependent not only on exposure to vitamin D, but also on concomitant intakes of calcium and phosphorus! January 5, 2022 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. 7

Vitamin D hypersensitivity • Vitamin D hypersensitivity has been proposed as the basis for Williams-Beuren syndrome. • It is a rare (1: 47, 000) condition of hypercalcemia and calcium hyperabsorption. • The syndrome is manifested in infancy. • It is characterized by failure to thrive with mental handicap and long-term morbidity. January 5, 2022 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. 8

Vitamin D hypersensitivity Patients have been found to have normal circulating levels of 25 -OH-D 3, but they appear to have exaggerated responses to oral doses of vitamin D 3. January 5, 2022 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. 9

Literature • Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. January 5, 2022 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. 10