[Vitamin D – from the past antirachitic factor to new pleiotropic substance].

Vitamin D is known for almost 100 years. Since time of its discovery, numerous studies on vitamin D function in the human body were performed. Considered from the beginning as an important factor in rickets prevention, thanks to the continuous development of knowledge, vitamin D is regarded now as an important factor from the point of view of the whole body homeostasis. Newly-find features of vitamin D allow to use this substance concentration in serum as a biomarker of general health and create opportunities of vitamin D use in the prevention and treatment of many diseases. The aim of this article is to present basic function of vitamin D in human body, sources of this substance, its metabolism and molecular mechanism of action, taking into account the evolution of the state of knowledge about Vitamin D - from early researches leading to its discovery, through the finding of its basic functions to the present studies on vitamin D mechanisms of action at molecular and genomic level.