I'm a transgirl, and have been on spiroactone for about 10 months early in hormone therapy. I've since been switched to cyproterone.
As others have mentioned, Spiro wont reduce the NUMBER of hairs, especially on the face and groin areas. On the body especially the legs and arms it will do two things, lighten the hair and reduce it's thickness. I'm on 100 mg twice daily , or was, and I went from having very typical male legs to typically female pattern.
Some caution is required with Spiro. The first thing you are likely to notice is you will need to use the bathroom about twice as often. Spiro is basically a water pill and will make you have to pee alot. It's important threfore that you intake enough fluids to compensate so you dont become dehydrated. The second side effect is that it greatly affects blood pressure, in that it lowers it. You can notice busy spells, especially when you sit up rapidly froma sitting or kneeling position. Finally, it causes issues with potassium levels , so you have to watch your diet and avoid high potassium items like bananas.Blood work to check your levels at least once every 6 months is necessary .
Cyperoterone is a much stronger antiandrogen. However like all antiandrogens it can be hard on the liver. Most endocrinologists start you on spiro first to make sure you can tolerate the antiandrogens.When I was switched I was grreatly relieved at the reduction in the number of bathroom trips. I swear I couldnt leave the house for five minutes before.
As others have mentioned, it wont reduce the number of hairs or thickness on the face. It WILL however prevent new facial hair growth that was being enacted by the higher testosterone levels. Elcectrolysis is the preferred method to remove what is already growing. Sometimes you can get it cheaper at beauty schools.