Fierce, you didn't say if your reading was:
"Total (LC/MS/MS)" or
"Free and Total (LC/MS/MS)" or
"Free, Bioavailable and Total (LC/MS/MS)"
Spironolactone blocks the body's testosterone receptors and so reduces the body's ability to use the testosterone in the system.
It does not completely stop the testes from producing testosterone. So you might try changing your dosing schedule to twice daily, or getting another medication from your endo, such as Casodex.