AGING SKIN

Aging of the skin is a composite of actinic damage, chronologic aging, and hormonal influences. The majority of changes associated with agin g, such as wrinkles and solar lentigines (''liver spots''), are due to photoaging and reflect cumulative sun exposure as well as skin pigmen tation. Classically, chronologic aging includes those cutaneous change s that occur in non-sun-exposed areas, such as the buttocks, and are o bserved in both men and women. A clinical example would be soft tissue sagging due to elastic fiber degeneration. In women, investigations i nto the effect of hormones on aging of the skin have concentrated on e strogens; in men, there have been a limited number of studies on the i nfluence of testosterone. The latter have Shown an age-dependent decre ase in tissue androgens in pubic skin, but not scrotal or thigh skin. To date, age has not been shown to have an effect on androgen receptor binding, although a decrease in foreskin 5 alpha-reductase activity w ith increasing age has been described. In fibroblast cultures from for eskins, there have been conflicting results as to whether 5 alpha-redu ctase activity decreases in an age-dependent manner. Some of the skin changes that have been categorized as secondary to chronologic aging, such as decreased sebaceous gland activity and decreased hair growth, may actually represent a decline in the concentration of tissue androg ens with increasing age. The influence of androgens on age-related cha nges in keratinocyte and fibroblast function remains speculative.