Sebaceous Glands and Sebum

Excess sebum is often associated with enlarged pores, follicle congestion, and an oily t-zone.  The sebum may also be thicker and stickier, making is harder to reach the surface of the skin.  

Testosterone is secreted by the body of men and women and enters the sebaceous glands, where the hormone 5-alpha reductase converts the testosterone into dihydrotestosterone, stimulating sebum formation. 5-alpha reductase is sensitive to hormone levels, it goes into over-drive when testosterone levels rise, creating excess oil production.  This is most commonly seen during puberty, but testosterone levels can be raised in some individuals throughout adult hood.