gynecology and obstetrics
Overview of Female Sexual Function and Dysfunction
Physiology
The traditional schema for the sexual response cycle includes the following: Desire (libido) Arousal (excitement) Orgasm Resolution Physiology of the female sexual response is incompletely understood but involves hormonal and central nervous system (CNS) factors. Estrogensinfluence sexual response.Estrogenhelps maintain genital tissue sensitivity, vaginal pH, normal microflora, elasticity, lubrication, and pelvic muscle tone. It is suspected but not proved that androgens are involved and act via androgen receptors andestrogenreceptors (after intracellular conversion oftestosteronetoestradiol). After menopause, ovarianestrogenproduction ceases, while ovarian androgen production varies. However, adrenal production of prohormones (eg, dehydroepiandrosterone sulfate [DHEAS]) that are converted to both androgens andestrogensin peripheral cells decreases starting in a woman’s 30s. Ovarian production of prohormones also declines after menopause. Overall, levels of androgen tend to stop decreasing at about age 60. Whether the decrease in sex hormone production plays any role in diminishing sexual desire, interest, or subjective arousal is unclear. The brain produces sex hormones (neurosteroids) from cholesterol, and production may increase after menopause. Whether this documented increase is universal, whether it facilitates arousal as peripheral production decreases, and whether it is affected by exogenous hormone administration are all unknown. A woman’s sexual response cycle is strongly influenced by her mental health and by the quality of her relationship with her partner. Initial desire typically lessens with age but increases with a new partner at any age. Desire is the wish to engage in sexual activity. There are many reasons for wanting sexual activity, including sexual interest. Sexual interest or desire may be triggered by thoughts, words, sights, smells, or touch. Desire may be obvious at the outset or may build once the woman is aroused. Brain areas involved in cognition, emotion, desire, and organization of genital congestion are activated. Neurotransmitters acting on specific receptors are involved. Based on known actions of medications and on animal studies, some neurotransmitters appear to be prosexual; they includedopamine,norepinephrine, and melanocortin. Serotonin is usually sexually inhibitory, as are prolactin and gamma-aminobutyric acid (GABA). This reflexive autonomic response occurs within seconds of a sexual stimulus and causes genital engorgement and lubrication. The brain's appraisal of the stimulus as biologically sexual, not necessarily as erotic or subjectively arousing, triggers this response. Smooth muscle cells around blood spaces in the vulva, clitoris, and vaginal arterioles dilate, increasing blood flow (engorgement) and transudation of interstitial fluid across the vaginal epithelium (lubrication). Women are not always aware of congestion; genital tingling and throbbing are more typically reported by younger women. As women age, basal genital blood flow decreases, but genital congestion in response to sexual stimuli (eg, erotic videos) may not. Peak excitement occurs; it is accompanied by contractions of pelvic muscles every 0.8 seconds and is followed by slow release of genital congestion. Thoracolumbar sympathetic outflow tracts appear to be involved, but orgasm is possible even after complete spinal cord transection (when a vibrator is used to stimulate the cervix). Prolactin, antidiuretic hormone (ADH), andoxytocinare released at orgasm and may contribute to the sense of well-being, relaxation, or fatigue that follows (resolution). However, many women experience a sense of well-being and relaxation without experiencing any definite orgasm. Resolution is a sense of well-being, widespread muscular relaxation, or fatigue that typically follows orgasm. However, resolution can occur slowly after highly arousing sexual activity without orgasm. Some women can respond to additional stimulation almost immediately after resolution. 