THE SEBACEOUS GLANDS 409 sebum as normal males, the glands can, however, be stimulated by adminis- tered testosterone (24). The stimulating action of androgens cannot be produced in the absence of the pituitary body, as shown by experiments in rats (25,26). It has been claimed that the necessary pituitary hormone is separable from other pituitary fractions, and it has been given the name of "Sebotropin" (27). The production of sebum by eunuchs appears to be correlated with the urinary excretion of 17-hydroxycorticoids and 17-oxosteroids (24) thus the activity of the sebaceous glands of eunuchs, who lack gonadal testo- sterone, appears to be dependent on adrenal androgens. The secretion of sebum by adult women is only a little less than that by normal men. Up to the age of 50 it is greater than in castrate men, but after that age it falls (23). This pattern suggests that the sebaceous glands in premenopausal women may be responding to androgens secreted not only by the adrenals but also from other sources. The ovary may be implicated, though it has not been possible to demonstrate any change in sebum secretion after bilateral ovariectomy (28). Oestrogens decrease the size of the sebaceous glands of animals (19-30), and reduce sebum production in man (3,4,31). When large amounts of oestrogen are given, however, the glands will still respond to small amounts of androgens given at the same time and thus oestrogens do not seem to antagonize androgens at their site of action. As they were unable to demonstrate a local, as distinct from a systemic, effect by local applica- tion of oestrogen (23), Strauss et al suggested the possibility that oestrogens could act systemically by suppressing endogenous androgen secretion. There are, however, several pieces of evidence against this view. Though it was possible to suppress sebum secretion in castrates by administration of oestrogen, the treatment appeared to have no parallel effect on the excretion of 17-hydroxycorticoids or 17-oxosteroids (24). Moreover, from animal experiments it appears that while the effect of androgens is produced by a stimulation of cell division and by an increase in the anabolic capacity of each sebaceous cell, oestrogens have different points of action. In rats which have been treated with oestrogen and androgen over the same period, the rate of cell division in the sebaceous glands is very little less than that in animals treated with androgen alone nevertheless, the sebaceous glands are smaller (32). Thus it seems that oestrogens decrease the size of the glands by increasing the rate of cell breakdown so that the synthetic potential is reduced, rather than by any interference with cell division. In addition, this action of oestrogens, unlike that of androgens, does not

410 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS depend on the presence of pituitary (33). Finally, the effect of oestrogens can be demonstrated in adrenalectomized or in spayed rats (32,33). In animal experiments oestrogens can thus be shown to act independently of androgens at the peripheral site and independently of tbe presence of androgen-secreting glands but this does not, perhaps, exclude the possi- bility that they could have some systemic action as well. The possible effect of progesterone on the sebaceous glands has been a matter of controversy. Some authors have stated that sebum production is increased during the luteal phase of the menstrual cycle (34), others that it has not (35), and the claim of Smith (36) that progesterone increases sebum production in elderly women is not consonant with other negative findings (35,37). Rothman et al published evidence that progesterone stimulated the sebaceous glands of spayed adult rats, claiming that its effect was comparable to that of testosterone (38). Although administra- tion of progesterone has been tried in a number of different circumstances, an effect of physiological doses has not been confirmed (39). However, some slight effect of progesterone may be detected in rats given the extremely large dose of 10 mg/day (40). CONCLUSIONS The evidence in support of the traditional view that the secretion of the sebaceous glands plays a part in maintaining the hydration and pliability of the stratum corneum and in inhibiting the growth of pathogenic fungi and bacteria is by no means conclusive. It is difficult nevertheless to accept the view that in man sebum is functionless and the sebaceous gland is vestigial. Over much of man's body the hair follicle is reduced to a vestige producing a wisp of veilus hair, and the arrector muscle is similarly degenerate. Yet it is in these very regions that the sebaceous gland shows its greatest development. If the sebaceous gland were truly vestigial and the sebum had no function, why has it not suffered the same fate as the apocrine gland, which becomes visible during development but subsequently disappears in most regions of the body ? Moreover, the sebaceous gland in both men and women has retained a response to male hormones no less sensitive than that of the accessory male sexual structures themselves. Zoological hypothesis would thus appear to be at one with the vested interest of the cosmetic chemist in maintaining a functional status for the gland. But why is sebum secretion so clearly linked with the sex hormones? Is the true function of the sebaceous glands and their product yet fully understood ? (Received: 23rd March 1965)