There is  no doubt that  the sebaceous gland  is  an androgen target organ. However, testosterone given to  an intact male adult had no further effect on SER, the  sebaceous glands being maximally stimulated, 3-4 though in 1974. Strauss et al have showed that pharmacological doses of methyltestosterone (100 mg/ day or more) will produce a small increase in sebum production.

Sebaceous glands in females are less than maximally stimulated, since a large dose of testosterone (100-200 mg/day) will increase sebaceous gland  size.  However,   relatively  small  doses  of androgens  given to  a prepubertal child  or  castrated adult produce  a marked increase of the SER. Not surprisingly, sebum production is decreased following castration has now been observed in women as well as in men.

This failure of oestrogen, whether administered systemically or applied locally, to maintain sebaceous gland inhibition in the face of androgen treatment, has suggested that its effect is not at the peripheral level of the sebaceous gland. Moreover, sebum-suppressive doses of oestrogen reduce  the  plasma  and urine  levels  of testosterone. Thus,  oestrogen  seems to decrease the amount of androgen reaching the  sebaceous gland and thereby reduces sebum output.

 

  Despite these apparently overwhelming facts indicating that oestrogens  have no  direct effect  on  sebum production,  there is some evidence to support the statement that oestrogens may have a local inhibitory action.

Firstly, the oral administration of ethinyloestradiol to castrated males was shown to induce a significant degree of sebum inhibition without affecting adrenal androgens,  as measured by the  urinary excretion  of 17-ketosteroids. However, the oestrogen might  have acted on sites other than the adrenal gland. Secondly, the local application of testosterone does not produce a significant or consistent increase in sebum production after  oral oestrogen suppression, and  so some  local inhibition by oestrogen may be operative.5 However, the evidence for an  indirect  effect  of  oestrogens on sebum production through the pituitary gland is inescapable.

 

  The role of progesterone on sebum excretion rate is conflicting and much of the quantitative information is from  animal experiments. Jarrett10 and Strauss and Kligman15 found no significant effect of progesterone on the SER in humans.  Ebling16 found no  effect of progesterone in rats but Thody and Shuster showed, in rats, that the endocrine environment during early life is an important factor in determining the adult response to progesterone.

  From the clinical viewpoint, Zeligman and  Hubener induced acne in ten out of eleven normal women  with 50 mg progesterone daily.18 Furthermore, Pochi investigated a patient with premature  ovarian failure  and, with the use of replacement therapy, demonstrated that the premenstrual flare of acne is most likely a progestational effect.19 However, no investigations of  sebum excretion were performed in these two studies.

 

  Topical progesterone (5  per  cent) will not  suppress sebum excretion  in males. Females with  a high  or intermediate SER  show a suppression of up to  25 per cent  at two months,  but  the effect  is less  after three months .20 The explanation for this  phenomenon, which has also been demonstrated in animals, is not known.  In these studies it was not due to a failure of application or to loss of bioavailability in the preparation.