Cholesterol is the precursor of the five major classes of steroid hormones.The synthesis of steroid hormones is initiated by the removal of a six-carbon unit  from  carbon  20  of  the  cholesterol  side  chain  to  form  pregnenolone,  the ordinary   precursor   of  all  steroid   hormones.  A  series   of  reactions catalyzed  by  cytochrome  P450  change  pregnenolone  to  give  increase  to  the  individual hormones.

   Figure:  Biosynthetic pathway for the synthesis of the steroid hormones.