It is taken from www.propeciahelp.com
You should focus more on the importance of progesteron and the way it is metabolised in a body.
5AR deficiency/lack elevates progesteron and drops down its metabolism necessary to produce sufficient amounts of neurosteroids. Direct mechanism is progesteron—>5AR----->5alfanorprogesteron—>Allopregnolon + GABA activates
(here come most of the mental negative feedback)
Testosteron---->5AR----->DHT (here most of the sexual sides occur)
The proper action must take place in a brain. When 5AR is defficient you are turned to be more like a midle age man or even worse.
PS. Sorry for accusing Dr.Shippen for writing this, but the progesteron backround looks to be reliable and logical.