The ingestion of excessive amounts of vitamin D<sub>3</sub> (or vitamin D<sub>2</sub>) results in hypercalcemia and hypercalciuria due to the formation of supraphysiological amounts of 25-hydroxyvitamin D [25(OH)D] that bind to the vitamin D receptor, albeit with lower affinity than the active form of the vitamin, 1,25(OH)<sub>2</sub>D, and the formation of 5,6-trans 25(OH)D, which binds to the vitamin D receptor more tightly than 25(OH)D. In patients with granulomatous disease such as sarcoidosis or tuberculosis and tumors such as lymphomas, hypercalcemia occurs as a result of the activity of ectopic 25(OH)D-1-hydroxylase (CYP27B1) expressed in macrophages or tumor cells and the formation of excessive amounts of 1,25(OH)<sub>2</sub>D.
Variants of selected polymorphisms: -1260/ C>A in CYP27B1, Lys198Asn in EDN1, and Ile105Val in GSTP1, were examined to determine if they confer susceptibility to sarcoidosis, based on an analysis of 180 Slovenian patients in comparison with 283 healthy controls.