Vitamin D and systemic lupus erythematosus: an update.

Vitamin D is a steroid hormone that, in addition to its actions on calcium and bone metabolism, exhibits a plethora of regulatory effects on growth, proliferation, apoptosis and function of the cells of the immune system that are relevant to the pathophysiology of systemic lupus erythematosus (SLE). Hypovitaminosis D is highly prevalent in SLE as a result of avoidance of sunshine, photoprotection, renal insufficiency and the use of medications such as glucocorticoids, anticonvulsants, antimalarials and the calcineurin inhibitors, which alter the metabolism of vitamin D or downregulate the functions of the vitamin D receptor. Low levels of vitamin D correlate with disease activity, and is associated with osteoporosis, fatigue and certain cardiovascular risk factors in SLE patients. This review updates the recent evidence on the relationship between vitamin D status and the onset, activity and complications of SLE, and summarizes the recommendations for vitamin D supplementation.