Selective modulation of sex steroids.

Recent evidence suggest that Sex Steroid Therapy involving estrogen while beneficial, may have adverse effects as well. Both of the known estrogen receptors, estrogen receptor-alpha (ER-alpha) and estrogen receptor-beta (ER-beta) have been found in reproductive tissues as well as bone, liver, and brain. These receptors are important targets for endogenous estrogen, estrogen replacement therapy and pharmacological estrogen agonists allowing specific modulation of sex steroids. This article will review the basic mechanisms of sex steroid biosynthesis and detail our current understanding of the action of these hormones on specific hormone responsive tissues. The properties of tibolone, a synthetic steroid will be outlined and its mechanism reviewed.