How does Spiro work?

[eftychia]

A web search turned up conflicting answers, so I now turn here ... Does spironalactone cause less testosterone to be produced in the body, or does it prevent cells from responding to testosterone that's still there (i.e. bind to testosterone-receptor sites so the testosterone can't)?

Or to put it another way: while I know that spironalactone reduces the effects of testosterone, will a blood test actually show less testosterone present, or will a test show the same or higher amounts of testosterone that's just no longer doing anything?

[xposted by hand to LL]