VDR and hypogonadism: However, even if the correlation between vitamin D and hypogonadism is not entirely clear, it must be considered that the expression of hydroxylases (CYP2R1 and CYP27B1) and VDR in testis tissue [47,62,63,64] also represents a further indication of the importance of the testicles in the metabolism of vitamin D [65,66,67].