Steroid formation in osteoblast-like cells.

For preventing the reduction of bone mass in postmenopausal women, oestrogen replacement is known to be useful and the importance of sex steroids in bone metabolism in both sexes is well established. The presence of steroid-converting-enzyme activities in various osteoblast and osteoblast-like cells has been demonstrated using in vitro culture systems. In the present study, we assessed the expression of messenger ribonucleic acid (mRNA) for aromatase, steroid sulphatase, 5 alpha-reductase, 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) and 3 beta-HSD by reverse transcription-polymerase chain reaction in the human osteoblast-like cell lines, MG 63 and HOS. Oestrogen, androgen and progesterone receptor mRNAs were also measured. Expression of mRNA for these enzymes and receptors was found in both cell lines without induction. From these and previous findings, we conclude that osteoblast-like cells have the capacity to form biologically potent oestrogens and androgens from peripheral circulating steroids. This may indicate an important role of bone in facilitating hormonal action.