Vitamin D Toxicity; Stored and Released from Adipose Tissue?

Vitamin D is a pro-hormone that plays an important role in body calcium regulation. Vitamin D toxicity occurs rarely due to its wide therapeutic index. A 38-year-old Iranian man was admitted to our hospital with a diagnosis of vitamin D toxicity. Laboratory test revealed hypercalcemia and elevated 25-hydroxyvitamin D (25(OH)D) level. Despite the cessation of vitamin D intake and diuretic treatment, he presented four months later with high 25(OH)D level and similar clinical features. Due to the potential release of vitamin D from adipose tissue, serial monitoring of 25(OH)D level is recommended.