Assessing vitamin D in the central nervous system.

Epidemiological and experimental evidence suggest that vitamin D deficiency is a risk factor for multiple sclerosis and other autoimmune diseases. The activated form of vitamin D exerts several immunomodulating properties in vitro and in vivo, that could contribute to explain the association with multiple sclerosis. Hypovitaminosis D is also associated with several other neurological diseases that is less likely mediated by dysregulated immune responses, including Parkinson's disease and Alzheimer's disease, schizophrenia and affective disorders, suggesting a more diverse role for vitamin D in the maintenance of brain health. Accordingly, both the vitamin D receptor and the enzymes necessary to synthesize bioactive 1,25-dihydroxyvitamin D are expressed in the brain, and hypovitaminosis D is associated with abnormal development and function of the brain. We here review current knowledge on the intrathecal vitamin D homeostasis in heath and disease, highlighting the need to assess vitamin D in the intrathecal compartment.