Dht blockers............?

can u please tell me...tht does green tea stop hair fall by blocking dht...in if is does then how much time will it take to reduce my hairfall completely......?? shud it b used topically or shud it b drunk to stop hairfall completely....?plzzzzzz help...its vvv urgent..plzz suggest some othr ways. to control dht in hairs as i suffer from pcos n i m shedding hell lot of hairs.......plzzzzzzzzzzzzzzzzzzzzz