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.

­　　脱发是一个复杂的问题，科学家们还在摸索其中的因果。多数科学家认为，男性型脱发跟基因有关。一般来说，男性型脱发会从两侧太阳穴上方开始，直到出现典型的M形发际线。通常头顶也会开始脱发，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.

­　　这可能与身体处理某些雄性激素的方式有关。事实上，患有雄性秃的男性继承了对雄激素二轻睾酮的遗传易感性，从而导致毛囊缩小、毛囊寿命缩短，最后无法再长出头发。而毛囊最容易缩小的部位就是头顶和前额发际线。

­　　"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."

­　　维克福斯特皮肤科医生艾米?麦克迈克尔在接受邮件采访时表示：“许多男性只出现了发际线升高的问题。也有男性是头顶脱发。但大多数时候，这两者是同时发生的。脱发顺序是由基因决定的，每个人的基因都有些微不同，因此开始脱发的时间和脱发严重程度也不一样。”

­　　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.

­　　头部其他地方的头发似乎更加强健。男性头部后方之所以不会脱发，是因为基因决定这里的毛囊由干细胞组成，并不会脱发。也正因如此，植发时移植的是后脑部位的头发。

­　　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.

­　　科学家们正在利用这一点研究延缓或根治脱发的更有效疗法。目前，获得美国食品药品监督管理局批准的只有两种药物。米诺地尔（品牌名落健）局部直接外用于头皮刺激毛囊，能够在一定程度上延缓脱发速度，甚至促进头发再生长。另一种药物是非那雄胺（保法止），通过口服抑制雄性激素二氢睾酮的分泌，以延缓脱发并促进头发再生。