Pubic Skin Research Articles

The effects of progesterone and pregnanedione on the reductive metabolism of dihydrotestosterone in human skin

The enzymatic formation of 5α-androstane-3α,17β-diol(3α-diol) and of 5α-androstan-3β,17β-diol(3β-diol) after incubation of [1,2- 3H]-dihydrotestosterone (DHT) was studied in the presence of progesterone and of its 5α-metabolite:5α-pregnane-3,20-dione (DHP) in pubic skin samples from women. Progesterone and DHP inhibit these two enzymatic activities both in the cytosolic and microsomal cellular subfractions. Progesterone does not seem to act as a classical competitive inhibitor whereas DHP is a competitive inhibitor for both 3α- and 3β-hydroxysteroid dehydrogenases (3α- and 3β-ketoreductases). p]The kinetic constants of both 3α- and 3β-ketoreductases towards progesterone and DHP were evaluated. Lineweaver and Burk plotting of the data showed, respectively for the two enzymatic activities, K i (progesterone) of 5.5 × 10 −5 M and 6.6 × 10 −5 M in the presence of NADPH, and K i (progesterone) of 5.0 × 10 −5 M and 3.5 × 10 −5 M in the presence of NADH; K ifi (DHP) of 1.1 and 1.25 × 10 −5 M in the presence of NADPH, and K i (DHP) of 1.0 and 0.95 × 10 −5 M in the presence of NADH. Moreover, progesterone was not a substrate for these enzymes whereas DHP was actively converted to its 3α- and 3β-hydroxy-metabolites: 3α-Hydroxy-5α-pregnane-20-one and 3β-Hydroxy-5α-pregnane-20-one. p] In view of the accumulating evidence that 3α- and 3β-diol could play an important role in the androgen target organs, the inhibition by progesterone and DHP of both 3-ketoreductase activities in human skin could have clinical implications.

ANDROGEN PRODUCTION AND SKIN METABOLISM IN HIRSUTISM

The concentrations of testosterone, androstenedione and dihydrotestosterone (DHT) in the plasma and 5α-androstane-3α,17β-diol (androstanediol) in the urine were measured in 40 women with hirsutism of ovarian, adrenal and idiopathic origin. Conversion of [3H]testosterone to DHT, 3α- and 3β-androstanediols was also studied in homogenates of pubic skin obtained from 15 of the patients. Results were compared with values obtained from normal men and women. Values for the levels of testosterone, DHT and androstenedione in the plasma and androstanediol in the urine of hirsute women were all above control levels, especially for plasma androstenedione and urinary androstanediol (P < 0·001). This finding was particularly marked in patients with hirsutism of ovarian origin. Conversion of [3H]testosterone to 5α-reduced metabolites by homogenates of skin obtained from hirsute women was significantly greater than by homogenates of skin from normal women (P < 0·001) but was the same as the value for normal men. The highest values for conversion were obtained from the patients with idiopathic hirsutism. These results indicate that androstenedione is the principal androgen secreted in hirsutism. In sexual skin this steroid may be converted to DHT and 3α-, and 3β-androstanediols and the increased activity of testosterone 5α-reductase may result in an exaggerated 'utilization' of androstenedione in this tissue. The high rate of excretion of androstanediol in the urine of patients with idiopathic hirsutism may be explained by the fact that this steroid is an end-product of testosterone metabolism.

A study of the in vitro metabolism of androgens by human scalp and pubic skin.

The metabolism of dehydroepiandrosterone, androstenedione and testosterone was compared in vitro in human scalp, forehead, pubic and axillary skin biopsies. Conversion of testosterone to the metabolite 5alpha-dihydrotestosterone, believed to be the active form of androgen, occurred in all tissues; however 17-oxosteroids such as androstenedione, 5alpha-androstanedione and androsterone were also formed from testosterone and were the major metabolites of scalp and forehead skin. While 17beta-hydroxy steroid dehydrogenase activity was present in every skin sample, it was evident there were differences in the direction of operation of this enzyme in skin from different body sites. Axillary skin readily metabolised androstenedione and dehydroepiandrosterone to active 17beta-hydroxy steroids such as testosterone and 5alpha-dihydrotestosterone, but these compounds were minor metabolites of androstenedione and dehydroepiandrosterone in forehead and scalp skin despite their activity in 17beta-oxidation of testosterone. Pubic skin was intermediate between axillary and scalp skin in its ability to form 17beta-hydroxy products from androstenedione and dehydroepiandrosterone. It is suggested these patterns of metabolism may reflect differences in androgen sensitivity.

Testosterone 5alpha-reduction in the skin of normal subjects and of patients with abnormal sex development.

Human pubic skin was obtained from normal subjects and patients with abnormal sex differentiation. Skin samples (200 mg) supplemented with NADPH, were incubated for 1 h with labelled testosterone. The conversion of testosterone to dihydrotestosterone, 3alpha- and 3beta-androstanediol was calculated. This conversion averaged 14.9 plus or minus 3.4% (SE) in 11 normal men and 3.6 plus or minus 1.4% (SE) in 8 normal women. In 4 children as in 4 young hypogonadotrophic hypogonadal men, the conversion rate of testosterone to 5alpha-reduced metabolites was low (0.8 to 3.5%) and increased at puberty (13.5 to 19.2%). After administration of HCG for 3 months to 1 of the hypogonadal men, it reached 30.2%. Inversely, the formation of dihydrotestosterone and androstanediols from testosterone was suppressed in 2 men treated with large doses of oestrogen. In 3 subjects with an incomplete form of testicular feminization syndrome, the conversion rate of testosterone to 5alpha-reduced metabolites was in the normal male range (6.4 to 18.3%), whereas it was low in one case of the complete form of the syndrome (1.5%). In 9 women with idiopathic hirsutism the rate of 5alpha-reduced metabolites recovered from testosterone was close to that of normal men (13.5 plus or minus 5.5% (SE). From these results, it is postulated that in human subjects, there is a good correlation between hair growth in skin from a sexual area and the extent of testosterone 5alpha-reduction in this tissue. Such an enzymatic activity might be induced by active androgens; this latter hypothesis is in good agreement with the increase of 5alpha-reduction activity observed at puberty or after treatment of young hypogonadal males. In addition, it is pointed out that a positive correlation is observed between the 5alpha-reductase activity present in each skin sample studied and the urinary 3alpha-androstanediol found for the same individual. This confirms our previous findings suggesting that the determination of urinary 3alpha-androstanediol might prove of clinical interest in the evaluation of the androgenic status in human subjects.

Metabolic studies in a patient with testicular feminization syndrome

The in vitro metabolism of radioactive labeled testosterone and androstenedione by a minced preparation of pubic skin from a patient with the complete testicular feminization syndrome was studied. Double-labeled 5α-dihydrotestosterone and 5α-androstanedione were identified, and 5α-reductase activity was found to be quantitatively similar to that of the pubic skin from a normal subject. The in vivo effect of 5α-dihydrotestosterone-propionate was also studied in this patient with the use of two normal subjects as controls. A sharp decrease in urinary levels of phosphorus and nitrogen was noted in normal subjects, whereas in the patient absence of response to the esterified 5α-reduced testosterone was observed. These results give further support to the concept that the testicular feminization syndrome is not due to a 5α-reductase defect.

Biochemical studies on the incomplete form of testicular feminization syndrome

The in vitro metabolism of tritiated-testosterone and 14C-androstenedione in public skin from two patients with the so-called incomplete form of Testicular Feminization Syndrome has been studied, and the following double-labeled metabolites were isolated: 5 α-dihydrotestosterone, 5 α-androstanedione, androsterone, testosterone and androstenedione. Biotransformation to 5 α-reduced steroid metabolites was not decreased as compared with pubic skin from a normal male and a normal female, thus indicating the presence of an active Δ 4-5 α-3-keto steroid oxidoreductase. The endocrine activity of the gonadal tissue from one of these patients was assessed by the in vitro formation of androgens from pregnenolone, dehydroepiandrosterone and their corresponding ester sulfates. In addition, the intramuscular administration of 5 α-dihydrotestosterone propionate had neither ostensible virilizing effect nor gonadotropin inhibitory activity on these patients.