Women go bald much less often than men its pretty large difference, and most women just thin out they dont actually get bald spots. Its like a third of women lose some hair, but for men its much higher even at younger ages. Which really does lend some credibility that male hormones are major players in male pattern baldness because what else really separates men and women?
The problem is propecia lowers DHT sure, but how much does higher estrogen protect hair for women? There are other hormones at play too