Table 2.

Causes of Vitamin D Deficiency58

Reduced skin synthesisSunscreen, skin pigment, season/latitude/time of day, aging, skin grafts
Decreaseed absorptionCystic fibrosis, celiac disease, whipple disease, Crohn disease, gastric bypass, medications that reduce cholesterol absorption
Increased sesquestrationObesity
Increased catabolismAnticonvulsant, glucocorticoid, highly active antiretroviral treatment, and some immunosuppressants
Decreased synthesis of 25-hydroxyvitamin DHepatic failure
Increased urinary loss of 25-hydroxyvitamin DNephrotic proteinuria
Decreased synthesis of 1,25-dihydroxyvitamin DChronic renal failure
Heritable disordersGenetic mutations causing rickets, or vitamin D resistance
Acquired disordersTumor-induced osteomalacia, primary hyperparathyroidism, hyperthyroidism, granulomatous disorders such as sarcoidosis, tuburculosis, and some lymphomas