The second member of “the big three” and another extremely effective FDA approved hair loss treatment is minoxidil. Minoxidil was originally an oral medication for high blood pressure. But after a while, patients started reporting hair growth — all over their bodies. And not much longer after, the minoxidil topical solution for treating hair loss was born.
In either sex, hair loss from androgenetic alopecia occurs because of a genetically determined shortening of anagen, a hair's growing phase, and a lengthening of the time between the shedding of a hair and the start of a new anagen phase. (See "Life cycle of a hair.") That means it takes longer for hair to start growing back after it is shed in the course of the normal growth cycle. The hair follicle itself also changes, shrinking and producing a shorter, thinner hair shaft — a process called "follicular miniaturization." As a result, thicker, pigmented, longer-lived "terminal" hairs are replaced by shorter, thinner, non-pigmented hairs called "vellus."