What does kind of dangerous side effects does DHT blockers has?

Increase Estradiol. Testosterone is converted into both Dht (dihydrotestosterone) & e2 (estradiol). Think of these two as balanced on opposite ends of seesaw. If you block/decrease dht, you could potentially increase e2. Too much e2 in men leads to moobs (man boobs), nipple sensitivity, gynecomastia, loss of libido, erectile dysfunction, etc.