Activity of Type 1 5α-Reductase Is Greater in the Follicular Infrainfundibulum Compared with the Epidermis
February 1997
in “
British Journal of Dermatology
”
type 1 5α-reductase type 2 5α-reductase follicular infrainfundibulum epidermis pilosebaceous unit androgens follicular keratinization acne vulgaris hirsutism male-pattern hair loss sex steroid hormone metabolism type 1 5-alpha-reductase type 2 5-alpha-reductase hair follicle skin oil gland male hormones hair growth acne excessive hair growth androgenic alopecia hormone processing
TLDR The enzyme type 1 5α-reductase is more active in the hair follicle's lower part than in the skin's outer layer.
The study, conducted on 82 normal subjects, found that type 1 5α-reductase enzyme activity is significantly higher in the follicular infrainfundibulum than in the epidermis. This was observed by measuring enzyme activity in isolated infrainfundibular segments, homogenized epidermis, and microdissected segments of the pilosebaceous unit. The enzyme activity was notably greater at pH 7, indicating the presence of type 1 5α-reductase isozyme. Additionally, the lower follicle showed higher activity at pH 5, suggesting the activity of type 2 isozyme. These results imply that androgens may play a role in follicular keratinization and could be important in understanding conditions like acne vulgaris, hirsutism, and male-pattern hair loss, highlighting the pilosebaceous unit as a key site for sex steroid hormone metabolism in the skin.
