禿頭，為啥禿的都差不多呢

You've seen the commercials or spotted it on your nearest and dearest — the loss of hair on the front or top of a head while a fringe remains around the chrome dome. Male pattern baldness (MPB), known in scientific circles as androgenetic alopecia, is responsible for more than 95 percent of male hair loss. Indeed, MPB affects around 50 million American men, with more than half of men over 50 reporting at least some hair loss, a risk that only increases with age. So, with such a great number of people affected, why is the baldness pattern generally the same?

你肯定見過禿頭，不管是在廣告上還是身邊的人身上——頭頂或額頭上方的頭發(fā)掉光了，只剩下邊緣還有一圈頭發(fā)。男性脫發(fā)有95%是雄激素性脫發(fā)造成的。在美國，有5000萬男性受它影響;50歲以上男性中，脫發(fā)的人超過了一半，隨著年齡增長，禿頭的風(fēng)險(xiǎn)只會越來越高。那么，既然禿頭的男性這么多，禿了的頭頂為什么看上去都大同小異呢?

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 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. 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 – you guessed it – the crown and frontal hairline.

脫發(fā)的原因很復(fù)雜，有一些問題科學(xué)家也還沒搞清楚。但很多人都認(rèn)為雄激素性脫發(fā)跟遺傳基因有關(guān)。首先，頭發(fā)一般會從兩側(cè)太陽穴上方開始脫發(fā)，最后發(fā)際線會變成一個(gè)經(jīng)典的“M”字。接著開始脫發(fā)的一般是頭頂。這種脫發(fā)模式可能與身體處理雄性激素的方式有關(guān)。事實(shí)上，患有雄激素性脫發(fā)的男性攜帶了對雄激素二輕睪酮非常敏感的基因，導(dǎo)致毛囊縮小、毛囊壽命縮短，最后無法再長出頭發(fā)。而毛囊最容易縮小的部位剛好就是頭頂和前面的發(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."

有些男性老了之后只會出現(xiàn)發(fā)際線后退現(xiàn)象，也有人是頭頂脫發(fā)，但大多數(shù)時(shí)候，這兩者是同時(shí)發(fā)生的。威克森林皮膚科的Amy McMichael博士在一次電子郵件采訪中說。這兩個(gè)部位的脫發(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 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," emails Dr. Marc Glashofer, a board-certified dermatologist and hair loss expert practicing in Northern New Jersey. "This is why hair transplants harvest the hair from the back of the scalp."

”而頭部后方之所以不會脫發(fā)，是因?yàn)槟抢锏拿沂怯筛杉?xì)胞組成的，并不會脫落。”一位在新澤西北部執(zhí)業(yè)的皮膚病專家和脫毛專家Marc Glashofer博士表示。也正是因?yàn)槿绱?，植發(fā)是通過移植后腦勺的頭發(fā)實(shí)現(xiàn)的。

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 or production of the disruptive androgen DHT, which slows hair loss and promotes hair growth. The drug has had a higher success rate than minoxidil.

科學(xué)家正利用這一點(diǎn)研究治療或延緩脫發(fā)的更有效療法。目前，得到美國FDA認(rèn)證的藥物只有兩種。一是敏樂啶(minoxidil)，可以直接外用與頭皮，能夠延緩脫發(fā)速度，甚至促進(jìn)頭發(fā)再生長。另一種則是非那雄胺(finasteride)，可以通過口服抑制脫發(fā)，這種藥的成功率比敏樂啶更高。