BDNF and Parkinson disease: Indeed, vitamin D is necessary for regulation of some neurodegenerative processes such as neurotrophin, inducible nitric oxide synthase (iNOS), glutathione and monoamine synthesis and also apoptosis.4, 5 These mechanisms are probable pathogenesis of some neurodegenerative diseases such as multiple sclerosis (MS) and Parkinson's disease (PD).6