This happens because of an excess of a chemical called dihydrotestosterone, or DHT, which causes the hair follicles to make thinner and thinner hair until they eventually pack up completely.

• 这是因为一种叫二氢睾酮的化学物质分泌过多导致头发卵泡化（？）而使头发逐渐变疏直到全部脱落为止（？）。