EFFECT OF ORAL ISOTRETINOIN TREATMENT ON SKIN ANDROGEN RECEPTOR LEVELS IN MALE ACNEIC PATIENTS

An oral daily dose (mean +/- SD, 0.75 +/- 0.05 mg/kg) of isotretinoin was administered for 3 months to six male patients with acne (scores of 4 and 5 according to Rosenfield). The therapy resulted in complete resolution of acne in four patients and improved acne significantly (score 1) in two patients. In accordance with recent findings, no change in serum testosterone and significant decreases in 5 alpha-dihydrotestosterone, 5 alpha-androstane-3 alpha,17 beta-diol glucosiduronate, and androsterone glucosiduronate levels were observed after treatment. Androgen receptor status was investigated in back skin biopsies obtained in acne areas before and after 3 months of isotretinoin treatment. The treatment did not modify the binding affinity constant of skin androgen receptor (0.44 vs. 0.32 nmol/L), but it did induce a 2.6-fold decrease in its binding capacity constant (62 vs. 24 fmol/mg cytosolic protein), as assessed by Scatchard plot and confirmed immunologically by Western blot analysis. These data clearly showed that skin androgen receptor was sensitive to oral isotretinoin administration in acneic patients. The decrease in skin androgen receptor levels (this study) and the recently reported suppression of skin 5 alpha-dihydrotestosterone production by isotretinoin treatment appeared consistent with the involvement of androgen receptor and 5 alpha-dihydrotestosterone in the pathogenesis of acne. Indeed, sebum production is under androgen control, and an abnormal response of the pilosebaceous unit to androgens appears to be implicated in the pathogenesis of acne. These observations were consistent with the absence of sebum in complete androgen-insensitive patients and normal sebum production in male pseudohermaphrodites.