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(fā)是一個(gè)復(fù)雜的問題，科學(xué)家們還在摸索其中的因果。多數(shù)科學(xué)家認(rèn)為，男性型脫發(fā)跟基因有關(guān)。一般來說，男性型脫發(fā)會(huì)從兩側(cè)太陽(yáng)穴上方開始，直到出現(xiàn)典型的M形發(fā)際線。通常頭頂也會(huì)開始脫發(fā)，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(guān)。事實(shí)上，患有雄性禿的男性繼承了對(duì)雄激素二輕睪酮的遺傳易感性，從而導(dǎo)致毛囊縮小、毛囊壽命縮短，最后無法再長(zhǎng)出頭發(fā)。而毛囊最容易縮小的部位就是頭頂和前額發(fā)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(yī)生艾米?麥克邁克爾在接受郵件采訪時(shí)表示：“許多男性只出現(xiàn)了發(fā)際線升高的問題。也有男性是頭頂脫發(fā)。但大多數(shù)時(shí)候，這兩者是同時(shí)發(fā)生的。脫發(fā)順序是由基因決定的，每個(gè)人的基因都有些微不同，因此開始脫發(fā)的時(shí)間和脫發(fā)嚴(yán)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(fā)似乎更加強(qiáng)健。男性頭部后方之所以不會(huì)脫發(fā)，是因?yàn)榛驔Q定這里的毛囊由干細(xì)胞組成，并不會(huì)脫發(fā)。也正因如此，植發(fā)時(shí)移植的是后腦部位的頭發(fā)。

­　　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(xué)家們正在利用這一點(diǎn)研究延緩或根治脫發(fā)的更有效療法。目前，獲得美國(guó)食品藥品監(jiān)督管理局批準(zhǔn)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(fā)速度，甚至促進(jìn)頭發(fā)再生長(zhǎng)。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(fā)并促進(jìn)頭發(fā)再生。