Men and women with hair loss often ask me why their hair is thinning. In most cases hormones are to blame. Dihydrotestosterone (DHT) is the culprit in men, while DHT and other hormones can cause hair loss in women. If you inherit hair follicles that are sensitive to these hormones, the result is a condition called androgenetic alopecia, better known as male pattern baldness and female pattern hair loss. Androgenetic alopecia affects more than 50 million men and 40 million women in the United States, making it the most common cause of hair loss by far.
What is DHT?
DHT is a naturally-occurring by-product of testosterone, the male sex hormone. An enzyme in the hair follicle’s sebaceous (oil) glands helps convert testosterone to DHT. This process happens in both men and women, even though women have less testosterone than men.
How Does DHT Cause Hair Loss?
To understand how DHT causes hair loss, it helps to understand the hair growth cycle. The cycle includes four phases: growing (anagen), transitional (catagen), resting (telogen) and shedding (exogen). DHT builds up in the hair follicles over time, disrupting the growth cycle. In a process called miniaturization, DHT shrinks hair follicles causing strands to reproduce at a slower rate by either shortening the growing phase or lengthening the resting phase. As androgenetic alopecia progresses and DHT continues to adversely affect the follicles, hairs become thinner, more fragile and often lighter in color with each subsequent life cycle. Eventually, the follicles shut down and will no longer produce hair.