There is considerable evidence that the male hormone, testosterone, plays an important role in sexual arousal. It seems to be more important in the sexual functioning of men than women, however. In women, the hormone estrogen affects sexual function, promoting vaginal lubrication and elasticity. After menopause, estrogen levels drop off dramatically in women, causing vaginal dryness and sometimes pain during intercourse. Hormone replacement therapy, which increases the level of estrogen, can moderate these negative effects although there are safety problems associated with long-term use.