Hair loss is complicated, and scientists are still trying to work out the bugs on why and how it happens. Pretty much all of them agree that Male pattern baldness (MPB) is usually genetic. Typically, loss begins above both temples, receding until a characteristic "M" pattern emerges. Often, but not always, the crown also starts to lose hair.

­　　脫發是一個復雜的問題，科學家們還在摸索其中的因果。多數科學家認為，男性型脫發跟基因有關。一般來說，男性型脫發會從兩側太陽穴上方開始，直到出現典型的M形發際線。通常頭頂也會開始脫發，但并非所有人都是如此。

­　　This is likely due to changes in how the body processes certain androgens, the male sex hormones. In fact, men with MPD actually inherited a genetic sensitivity to the androgen dihydrotestosterone (DHT). This sensitivity causes hair follicles to miniaturize, which shortens their life span and eventually leads them to stop growing hair. The areas most often affected by miniaturization are the crown and frontal hairline.

­　　這可能與身體處理某些雄性激素的方式有關。事實上，患有雄性禿的男性繼承了對雄激素二輕睪酮的遺傳易感性，從而導致毛囊縮小、毛囊壽命縮短，最后無法再長出頭發。而毛囊最容易縮小的部位就是頭頂和前額發際線。

­　　"Many men have frontal hairline recession only. Others will have thinning in the vertex (crown) of the scalp. Many times, both happen at the same time," says Dr. Amy McMichael with the Wake Forest Department of Dermatology in an email interview. "The order is predicted by genetics and each person has slightly different genetics that determine when hair will begin to thin and how severe hair loss will be."

­　　維克福斯特皮膚科醫生艾米?麥克邁克爾在接受郵件采訪時表示：“許多男性只出現了發際線升高的問題。也有男性是頭頂脫發。但大多數時候，這兩者是同時發生的。脫發順序是由基因決定的，每個人的基因都有些微不同，因此開始脫發的時間和脫發嚴重程度也不一樣。”

­　　The rest of the hair on the head is made of hardier stuff, apparently. The reason why men do not lose hair in the posterior scalp is that these follicles are genetically programmed to be stem cells and do not shed. This is why hair transplants harvest the hair from the back of the scalp.

­　　頭部其他地方的頭發似乎更加強健。男性頭部后方之所以不會脫發，是因為基因決定這里的毛囊由干細胞組成，并不會脫發。也正因如此，植發時移植的是后腦部位的頭發。

­　　Scientists are using this knowledge to develop more effective treatments to slow or stop hair loss. Currently, only two treatments are approved by the U.S. Food & Drug Administration. Minoxidil (brand name Rogaine) is applied topically, directly to the scalp to stimulate hair follicles. It has shown some success at slowing hair loss, even helping to re-grow hair. The other option is Finasteride (Propecia), which is taken orally to limit the production of the disruptive androgen DHT, which slows hair loss and promotes hair growth.

­　　科學家們正在利用這一點研究延緩或根治脫發的更有效療法。目前，獲得美國食品藥品監督管理局批準的只有兩種藥物。米諾地爾（品牌名落健）局部直接外用于頭皮刺激毛囊，能夠在一定程度上延緩脫發速度，甚至促進頭發再生長。另一種藥物是非那雄胺（保法止），通過口服抑制雄性激素二氫睪酮的分泌，以延緩脫發并促進頭發再生。