Chp 5: Hormonal Influences on Human Sex Behavior

1. Masters and Johnson (1966) divide the “human sexual response” into phases: sexual excitement: increased sexual arousal or excitement the male experiences penile erection (relaxation of smooth muscles within the corpora cavernosa, allowing for increased penile blood flow and rigidity) the female experiences pelvic vasocongestion (increased blood flow), vaginal lubrication, and swelling of the external genitalia plateau: state of heightened sexual excitement orgasm: peak of sexual arousal, characterized by physiological and psychological changes: rhythmic contraction of reproductive structures (in men, seminal emission and ejaculation), cardiovascular and respiratory changes, and a release of sexual tension sexual resolution (or satiety): refractory period--decreases in sexual desire and sexual performance these phases are the same between men and women, with the exception that men experience ejaculation but women do not Chp 5: Hormonal Influences on Human Sex Behavior

2. Effects of hormones on human sex behavior come from several types of studies: changes seen in “hypogonadal” individuals: removal of ovaries or testes in individuals for medical reasons (e.g., cancer) castration to control “inappropriate sexual activity”--treatment of sex offenders absence or presence of only low levels of hormones secreted (GnRH, LH, FSH, gonadal steroids); an example is Kallman’s syndrome changes seen during aging males secrete lower levels of testosterone as they age females also secrete lower levels of ovarian hormones as they age--the phenomenon of ”menopause” Gonadal steroids are not necessary, but can influence, human sex behavior sex steroids are less important for sexual performance sex steroids (androgens) play an important in enhancing sexual desire (“motivation”) in both men and women Hormonal Influences on Human Sex Behavior

3. Hormones are not critical to the performance, or experience, of a sexual act: In males: infant and prepubertal males can experience nocturnal erections thus, erections can occur when secretion of androgens are low hypogonadal adult men are capable of erections and orgasm absence (or low levels) of testicular androgens do not block ability to show erections in response to erotic stimuli, or to experience an orgasm absence (or low levels) of testicular androgens do reduce the display of “spontaneous” penile erections that occur during the day or night (nocturnal erections) administration of testosterone to hypogonadal adult men can increase the occurrence of “spontaneous” penile erections Hormones and Sexual Performance in Humans:

4. Hormones are not critical to the performance, or experience, of a sexual act: In women: menopause is associated with a decline in menstruation and in the production of ovarian hormones however, postmenopausal women can engage in normal sex behavior and experience orgasm the loss of ovarian hormones during menopause is associated with a decline in “normal vaginal functioning”: decrease in pelvic vasocongestion (blood flow) atrophy of vaginal epithelium diminished vaginal lubrication (increase coital pain) Hormones and Sexual Performance in Humans:

5. Hormones, in particular androgens, are important for sexual desire. “sexual desire” may be inferred by frequency of sexual thoughts and fantansies, interest in initiating sexual experiences, awareness of sexual cues In males: at puberty, males begin to show an increased interest in sexual activity associated with a rise in testosterone secretion hypogonadal adult men (low levels of testicular androgens or none) show decreased levels of sexual activity believed to be linked to decreased interest in sex behavior (decreased desire) Ex. individuals with Kallman’s syndrome Ex. individuals castrated for inappropriate sex behavior aged men (>75 years of age) show decreased levels of sexual activity associated with a decline in testosterone secretion Hormones and Sexual Desire in Humans:

6. Kallman’s Syndrome: (Ex. males) individuals in which GnRH neurons do not develop normally GnRH neurons do not migrate to medial preoptic area loss of control of anterior pituitary secretion (LH and FSH), and loss of secretion of gonadal steroids secretion (testosterone) from testes often identified at puberty when they do not go through normal changes in secondary sex characteristics without treatment, individuals report: disinterest in sex behavior, low levels of sexual activity, rarely experience “spontaneous” penile erections (day or night) after administration of exogenous androgens, these individuals report: increased sexual interest, spontaneous daytime and nocturnal penile erections, and eventually increased sexual activity Hormones and Sexual Desire in Humans:

7. Study by Heim (1981): effects of surgical castration as a method to treat incarcertated sex offenders design: 39 sex offenders from West Germany who agreed “voluntarily” to surgical castration prior to release sex offenders were classified as follows: 12 rapists (31%), 12 heterosexual pedophiliacs (31%), 4 homosexual pedophiliacs (10%), four bisexual pediophiliacs (10%), 6 homosexuals (15%), and 1 sex murdered (3%) following release they were mailed a questionnaire contained 46 items concerning the subjects’ sexual functioning before and after castration (time since released from prison--avg. 4.3 years, ranging from 4 months to 13 years) Hormones and Sexual Desire in Humans:

8. Study by Heim (1981): results: following castration, 56% of males no longer practiced masturbation or engaged in sex behavior (all reported a reduction or absence of sexual desire) of the 44% that still practiced masturbation or sex behavior, all reported a reduction in their sexual desire interesting sidelight: different percentages of males showed sex behavior following castration among the different types of sex offender: the former “rapists” were sexually more active after castration than homosexuals and pedophiliacs (50% of the 17 males that continued to show masturbation or sex behavior were the former “rapists”) interesting question: why do some castrates continue to engage in sexual activity while others do not? Answer--we don’t really know! Hormones and Sexual Desire in Humans:

9. Hormones, in particular androgens, are important for sexual desire. In females: at puberty, females begin to show an increased interest in sexual activity associated with ovarian activity-->secretion of estrogen and progesterone (and androgens) note: adrenal glands are also a source of androgens/estrogens/progestins link between ovaries and adrenals in sex behavior in women: removal of ovaries alone has been reported to have little effect on sexual interest or performance in the human female removal of the ovaries and adrenals (a procedure previously used to control cancer by removing all sources of estrogenic steroids) produces a drastic decrease in sexual desire and sex behavior Hormones and Sexual Desire in Humans:

10. Study by Sherwin et al. (1985): 58 surgically menopausal women (hysterectomy & bilateral removal of ovaries) Method: different groups of females received different hormone treatments: 1) hysterectomy control group (control, has ovaries present--ovarian hormones), 2) placebo group (no steroid), 3) estrogen only group, 4) estrogen plus androgen group, and 5) androgen only group asked to fill out a questionnaire daily--”indicate the degree of your sexual desire during the past 24 hours”; this included ratings of sexual arousal, sexual thoughts or fantasies, the number of specific sexual encounters with a partner, and the number of times orgasm was achieved Results: administration of androgen alone stimulated sexual desire and sexual fantasies, while administration of estrogen alone did not hormone regimen did not significantly affect frequency of sex behavior or orgasm Hormones and Sexual Desire in Humans:

12. In human females: estrogen: maintains vaginal functioning--vaginal lubrication; stimulates proliferative changes in uterus (for pregnancy) progesterone: stimulates proliferative changes in uterus (for pregnancy) androgens: stimulate sexual desire and thoughts (motivation) androgens are secreted from ovaries and adrenals suggested that the ovary and adrenal contribute equally to plasma concentrations of testosterone, dihydrotestosterone and androstenedione (all androgens), except at mid-cycle (periovulatory period) where the contribution of the ovary is twice that of the adrenal for androstenedione androgen levels increase during the periovulatory period (when estrogen levels rise) however, increased levels of androgens do not equate to increase levels of sex behavior--other factors can facilitate sex behavior (flowers & candy on Valentine’s day), or inhibit sex behavior (an upcoming exam)! Hormones and Sexual Desire in Humans:

13. Dopamine: evidence that increasing dopamine activity can increase sex behavior in humans one method of treating Parkinson’s patients (who have too little dopamine in nigrostriatal pathway) is to give them L-dopa, a drug that increases synthesis of dopamine administration of L-dopa to Parkinson’s patients enhanced the patient’s motor abilities as well as stimulating penile erections also, ingestion of drugs that increase dopamine activity (cocaine, amphetamines) can stimulate sex behavior--increased sexual desire and performance (short-term effect) evidence that blocking dopamine activity can decrease sex behavior in humans patients with psychotic symptoms (e.g., individuals with Schizophrenia) are treated with neuroleptic drugs that act to block dopamine activity (antagonists) side-effect of drug treatment: decreased interest in sex behavior and decreased performance (reduced ability to ejaculate) Neurotransmitters & Human Sex Behavior:

14. Oxytocin: oxytocin is released peripherally (within the bloodstream) during the orgasmic phase of the human sexual response in both men in women stimulate sperm transport in males and females by stimulating contraction of smooth muscle (other effects) evidence (in animals) that oxytocin may also be released within the brain; several effects have been associated with release of oxytocin centrally (within the brain): stimulation of sex behavior in males and females; in males, oxytocin levels increase with each ejaculation inhibition of sex behavior (high levels of oxytocin have been shown to inhibit sex behavior in males) formation of social bonds Neurotransmitters & Human Sex Behavior: