Two different pathogenetic mechanisms may play a role in acne and in hirsutism

Acne is one of the most common skin disorders. Androgens are known to play an important and possibly central role. Androgens secreted from ovaries and adrenal glands (androstenedione, dehydroepiandrosterone and its sulphate, testosterone) and target tissue-produced androgens (testosterone and its 5 alpha-reduced metabolite, dihydrotestosterone) have been implicated. Although the sebaceous gland and the hair follicle form a single morphological entity, the pilosebaceous unit, acne and hirsutism do not always appear concomitantly, thus leading to the supposition that these two structures may have different degrees of sensitivity to similar androgenic stimulation.

To determine whether acne and hirsutism are the clinical expression of a different androgen metabolism at target tissue levels we studied 90 randomly selected patients who came to our Out-patient Department for diagnosis and treatment during the last 2 years with isolated acne of mild to severe degree and 52 patients with idiopathic hirsutism without acne or history of acne. Twenty-four women without acne or hirsutism and without a history of endocrine disease were studied as controls.

In both groups of patients, plasma levels of sex hormone binding globulin, of dihydrotestosterone, and of 3 alpha-androstanediol and of its glucuronide were evaluated. In all patients the percentage of free testosterone and the testosterone/sex hormone binding globulin ratio were also calculated.

Patients with acne and those with isolated hirsutism showed significantly decreased sex hormone binding globulin plasma levels. The values of the percentage free testosterone and those of the testosterone/sex hormone binding globulin ratio were, on the contrary, higher with respect to the controls, although there were no statistically significant differences between the two groups. Significantly increased plasma levels of dihydrotestosterone with respect to the controls were observed in patients with acne or in those with hirsutism. However, while all patients with hirsutism showed increased plasma values of 3 alpha-androstanediol and its glucuronide, all patients with acne showed plasma levels within the normal range, independently of the precursor plasma levels.

Our results demonstrate that dihydrotestosterone is further reduced to 3 alpha-androstanediol and its glucuronide only in hirsute patients but not in acne patients. These results suggest that dihydrotestosterone may undergo different metabolic pathways at skin levels and support the hypothesis that the two clinical manifestations may be the expression of the different metabolic fate of dihydrotestosterone itself. Moreover, our results demonstrate that 3 alpha-androstanediol and its glucuronide cannot be used as plasma markers of target-tissue produced androgens in all hyperandrogenic conditions.