Why can only men grow bushy beards?

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Why can only men grow bushy beards?

In: Biology
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It’s a testosterone thing. Male hormones promote facial (and other) hair growth. That’s why it starts at puberty. Some women who have unusual hormonal situations can also grow beards, but most will take steps to remove their facial hair as it is societally frowned upon in western cultures.

Body hair growth is modulated by a signalling molecule in the body called DHT. DHT is manufactured from testosterone. Although women have some testosterone, men have a hell of a lot more of it, so a lot more to convert into DHT. Women could theoretically grow bushy beards if for example a mutation greatly increased testosterone levels or caused a bug in DHT processing that made low levels of DHT cause a lot more hair growth than intended. This is why trans men can naturally grow beards just from hormone replacement therapy: More testosterone is added to the body, which means more DHT, even though the genes that would produce testosterone are much less active.

They aren’t. Around 1 in 10 women, if not more than that, will develop facial hair to varying degrees. This is, as one example, due to developing polycystic ovarian syndrome (PCOS), which affects 18% of all women and has a common effect of hirsutism.