SEX HORMONES AND SKIN 391 Castrated and Castrated hypophysectom•zed ,5 a-- D•hydroteslosterone Testosterone Figure 4. Recovery of identified metabolites, expressed as percentage of total recovered radioactivity in skin samples, 1 h after injection of testosterone-4-•C into male rats. Each histogram represents results from a pool of 25-30 rats. response of the skin to androgens involves their conversion to active meta- bolites which is pituitary mediated, though more results are needed to substantiate the hypothesis. Finally, we come to body hair. The problem is usually not how to stimulate hair growth, but how to suppress it in women in which it occurs in culturally unacceptable amounts. While there is no doubt that the facial, axillary, pubic and body hair is all androgen dependent, growth of facial and body hair is often abnormal in women who show no apparent endocrine disturbance. Is it possible that this 'idiopathic' hirsutism is also related to peripheral androgen conversion? There is evidence that genital skin from both men and women is better able than general body skin to convert testosterone to 5a-dihydrotestosterone, and this is true for the foetus as well as the adult (35). But an even more interesting clue comes from a recent report that hirsute women excrete five times as much 5a-andro- stanediol as normal subjects (36). Does the growth of sexual hair perhaps depend on the conversion at site of endogenous androgens not only 5a- dihydrotestosterone but to the 5 a-androstanediols ? I have travelled a fair distance in my discourse, and the time has come

392 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Dehydroepiandrosterone Testosterone o Androstened ione • OH •"•oj•• • H 5-(-Dihyd rotestosterone OH 50- Andros tone -3 •,• 7,B-d iol o 5"-And ros taned ion e Androsterone Figure 5. Possible pathways of androgen metabolism in rat skin. Solid circles indicate compounds which have been clearly shown to have significant effects on sebum production in hypophysectomized-castrated rats open circles indicate compounds which have failed to do so the stippled circle indicates a small effect significantly demonstrated only by the use of a large number of rats. to summarize some of the details of the journey. I have drawn attention to those qualities of the skin, namely texture, appearance, feel and smell, which are concerned with sexual communication and discussed the under- lying mechanisms especially in relation to the epidermis, the sebaceous and apocrine glands, and the body hair. In man, no less than in other animals, these structures change at puberty and are all profoundly influenced by both male and female hormones. Sebum secretion, the growth of sexual