Microbial catabolism of phytosterol side chains yields C-19 steroids, C-22 steroids, and 17-ketosteroids (. precursors to adrenocortical hormones and contraceptives ).     The addition and modification of functional groups is key when producing the wide variety of medications available within this chemical classification. These modifications are performed using conventional organic synthesis and/or biotransformation techniques.  
The genetics of 21OHD have been well studied  . Currently more than 150 mutations in the CYP21A2 gene have been described (Human Gene Mutation Database Website, ; Human Cytochrome P450 (CYP) Allele Nomenclature Committee, / ), of which about 10 types account for 90% of affected alleles  . During the last two decades, screening for 21OHD has been included in neonatal screening programs in most industrialized countries. This has led to more accurate data concerning the distribution and the incidence of 21OHD in the various populations and ethnic groups. Mutation frequencies in different populations have been investigated and differences in specific ethnic groups described. However, exact data are still lacking.