Sexual interest in postmenopausal women is related to 5alpha-reductase activity.

Many studies to date have suggested a role for testosterone in women's interest in sex after the menopause. However, this does not appear to be related to serum concentrations of testosterone. Testosterone is converted to the more active dihydrotestosterone by an enzyme, 5alpha-reductase, found in target tissues. The activity of this enzyme has been shown to be variable, being more active in women with hirsutism and men with benign prostatic hypertrophy than in normal controls. We have shown that women complaining of a loss of interest in sex after the menopause have higher amounts of 5alpha-reductase activity, as reflected by urinary ratios of the 5alpha-product (androsterone) to the 5beta-product (aetiocholanolone) of androstenedione, than women with no loss of interest in sex after the menopause. However, of those women who noted a loss of interest in sex after the menopause, the women who responded to oestrogen replacement had higher amounts of 5alpha-reductase activity than those whose interest in sex did not improve with oestrogen replacement. The urinary aetiocholanolone:androsterone ratio may be predictive of which women will experience a loss of interest in sex following the menopause (natural or induced) and which of these women will respond to oestrogen replacement.