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ANDROGENS, LIBIDO, AND SEXUAL ACTIVITY

Although androgen hormones are often referred to as "male hormones", they are secreted by the adrenal glands in addition to the testes. As a result, androgens are normal hormones for both men and women, although the relative concentrations may vary. Androgens are synthesized from both the ovaries and adrenal glands and estrogens are synthesized by both the testes and adrenal glands. Some females actually produce more testosterone than some males (Rogers, 2001).
Hormones affect pubertal behavior; children that undergo precocious puberty (earliest menarche 17 months) show similar changes although none of their peers are. Castration decreases sexual activity from male (removing pituitary same effect in animals as castration). Castrated males have narrow shoulders & broad hips, thighs that converge, female fat distribution, and high pitched voice; less body hair & more scalp hair. Anti-androgens decrease sexual interest in male; some states use to treat convicted sexual offenders. Women retain their libido after menopause when their ovaries are inactive and even if their ovaries are removed. A loss of the adrenal glands (which secrete androgens), however, causes a loss of libido and androgens have been used to treat a lack of interest in sex (Moir, 1991).The major adrenal androgens are dehydroepiandrosterone-sulfate (DHEAS), androstenedione, testosterone, and dihydrotestosterone (Mahmoud, 2006). Testosterone is the precursor to estrogen and therefore, it is naturally present in female tissues as well as those of males. One of the actions of androgens is that mediate changes in the brain which affect mood and behavior.

In males, the production of testosterone increases in the male fetus early in the third month of development through birth. It mediates effects on the male genetalia and hypothalamus during this time. About 2 months after birth there is another surge in testosterone production which last several months although its significance is not understood. The final surge in testosterone production occurs during puberty where it contributes to growth, development of the primary sex organs and secondary sexual characteristics, and influences sexuality, personality, violence, and other cognitive aspects (Ramirez, 2003).

LIBIDO
Androgens increase sex drive in both men and women. Androgen levels are highest near the midpoint of the menstrual cycle, the time associated with an increase in female sexual activity. A decrease in the amount of androgen produced (associated with surgical removal of gonads, disorders of the adrenal glands and pituitary) will decrease libido. Decreased testosterone results in decreased libido, fatigue, and general depression of mood and androgen supplements can restore normal libido in men (Mahmoud, 2006).

The largest study done on female sexual dysfunction (FSD) concluded that it affects 43% of women in the United States. This study based on the U.S. National Health and Social Life Survey of 1992 also found that among women with FSD, 51% had low libido. This makes it the most prevalent female disorder (22% of all women), followed by arousal problem (33%) and pain disorders (16%) (Mahmoud, 2006). Androgens are used to treat low libido in women in general Androgens are used to treat the loss of libido in postmenopausal women (Genazzani, 2002; Mahmoud, 2006).

In order for the gonads to secrete steroid hormones after puberty, they need to stimulated by hormones from the pituitary gland (FSH and LH) which are in turn produced in response to a hypothalamic hormone GnRH. A number of mutations can interfere with this mechanism and cause hypogonadotrophic hypogonadism. Mutations may affect GnRH, the GnRH receptor, or the migration of the GnRH producing cells from their embryonic origin in the nose to the hypothalamus (Kallman's syndrome which also involves the inability to smell). Since the onset of puberty relies on the signal leptin and its receptor (among others), mutations in these genes delay the onset of puberty and cause hypogonadism (MacColl, 2002; Bulow, 2002). Male libido and interest in women is absent in men with Kallman syndrome which is caused by a failure of GnRH secreting cells to migrate from the nose to the brain (which then eliminates the signal to the pituitary which in turn eliminates the signal to the testes to make testosterone) (Pfaff, 1997).

The major androgen synthesized in the ovaries is androstendione and that of the adrenal glands is DHEA (dehydroepiandrosterone). These can be converted to testosterone by the liver and skin (Eriksson from Steiner, 2000).

SEXUAL ACTIVITY
Higher levels of sexual activity are correlated with higher levels of androgens. Testosterone levels increase during arousal and with masturbation in men and women, although they do not rise as significantly in women upon viewing erotic films (Van Anders, 2007). In women, testosterone levels rise before sexual activity and after cuddling (Van Anders, 2007).

Salivary testosterone levels are associated with levels of sexual activity in adolescent males (Pfaus, 1999). Testosterone levels are higher the morning after intercourse in men who mated with unfamiliar partners or multiple partners (Van Anders, 2007). Testosterone levels and the likelihood of masturbation are inversely associated with relationship commitment (Van Anders, 2007).

ORGASM
Testosterone and DHT levels are positively associated with orgasm in women and men. Women most frequently orgasm around the time of ovulation at which point estrogen and testosterone levels are highest (Mah, 2001). Testosterone levels rise after orgasm and are higher in women who experience orgasm than those who do not (Van Anders, 2007).

OTHER

Androgens also increase irritability in men and women. High levels of androgens may be associated with the irritability of some parts of the menstrual cycle in females (Steiner, 2003). In men, chemical castration is linked to increased risk of depression and anxiety. Ending chemical castration coincides with improved performance in memory. Decreased testosterone levels are linked to depression and testosterone supplementation improves some types of cognitive ability (Almeida, 2004).

Adrenal and ovarian levels of androgen decline in women as they age. Oral contraceptives can lower androgen levels by decreasing LH levels and by increasing the amount of sex hormone binding globulins (SHBG) which can bind androgens and make them less available. Glucocorticoids reduce ACTH secretion and thus androgen secretion (Mahmoud, 2006).

 

Estrogen therapy can also improve physical problems in sexual activity (such as inadequate lubrication, vaginal congestion, or muscle contraction) and libido (Mahmoud, 2006)