Male-pattern baldness, or androgenetic alopecia, means the hair follicle slowly, over time, becomes smaller. Testosterone becomes dihydrotestosterone in the hair follicle by an enzyme called 5-alpha-reductase. When the enzyme attaches to the androgen reception in the hair follicle, it causes it to produce smaller hair. Dr. Jennifer Chwalek, a dermatologist, explained genetics determines whether you lose your hair and how soon.