The Sexual Medicine Alphabet: “T” is for Testosterone
Testosterone falls within a class of sex hormones called “androgens,” which are thought to play a key role in maintaining sexual desire and other aspects of sexual function in both men and women. Testosterone may additionally play a role in a person’s sense of well-being, energy level, bone mass, muscle mass and strength.(1)

Although typically considered exclusive to males, testosterone is actually produced naturally by women in their ovaries and adrenal glands. Each produces about half of the total testosterone in a premenopausal woman.(2) Interestingly, pre-menopausal women produce three to four times more testosterone than estrogen,(3,4) yet the total amount is still only about five to 10 percent the amount found in men.(5)

However, not all circulating testosterone is available for use by the body. The majority of testosterone in the blood (as much as 80 percent) is strongly bound to a protein called Sex Hormone Binding Globulin (SHBG). This renders it biologically inactive.(6,7,8,9) The remainder of the testosterone (termed bioavailable testosterone) either circulates freely (termed free testosterone) or is loosely bound to another protein in the blood called albumin.

Testosterone Loss
Two primary causes of testosterone depletion are the natural aging process and surgical menopause (menopause caused by the removal of both ovaries). As women age, their bodies produce less testosterone; levels in women in their forties are estimated to be half that of women in their twenties.(10) Because the ovaries produce half the testosterone in a woman’s body, their surgical removal may result in as much as a 50 percent decrease in testosterone levels.(11,12,13)

Additional causes of decreased bioavailable testosterone levels include disease of or damage to the ovaries,(14,15) problems with adrenal glands (16,17) and the use of certain drugs and medications, including oral contraceptives (which increase SHBG production).(18)

Female Sexual Health
As early as the 1930s, experts began to observe that testosterone levels in women affect sexual desire.(19,20) In addition, growing evidence suggests that many women experience decreased sexual desire as their testosterone levels decline through the natural aging process or the surgical removal of the ovaries. Low sexual desire is the most prevalent female sexual health complaint and women are twice as likely as men to experience low sexual desire.(21) Hypoactive Sexual Desire Disorder (HSDD) can result if this loss of sexual desire results in marked personal distress.(22)


For Women Only
Unfortunately, there is little a woman can do to prevent testosterone loss, as many contributors to loss are unavoidable or necessary (such as the natural aging process, removal of the ovaries, and chemotherapy). Although there are products available that contain testosterone and testosterone derivatives, none has been approved for treating HSDD in women.

Yet studies on the use of testosterone in women are progressing, and scientists are optimistic that new research could finally lead to the emergence of treatments for HSDD.

Resources

(1) Bachmann GA, Bancroft J, Braunstein G, et al. Female androgen insufficiency: the Princeton consensus statement on definition, classification, and assessment. Fertil Steril 2002;77:660-65.
(2) Abraham GE. Ovarian and adrenal contribution to peripheral androgens during the menstrual cycle. J Clin Endocrinol Metab1974;39:340-346.
(3) Longcope C. Hormone dynamics at the menopause. Annals of the New York Academy of Sciences 1990;529:21-30.
(4)Laughlin GA, Barrett-Connor E, Kritz-Silverstein D, von Muhlen D. Hysterectomy, oophorectomy, and endogenous sex hormone levels in older women: the Rancho Bernardo Study. J Clin Endocrinol Metab 2000;85:645-651.
(5)Longcope C, Jaffe W, Griffing G. Production rates of androgens and estrogens in post-menopausal women. Maturitas 1981 Dec;3(3-4):215-23.
(6)Demers LM. Biochemistry and laboratory measurement of androgens in women. In: Redmond GP, ed. Androgenic disorders. New York: Raven Press, 1995:21–34.
(7)Longcope C. Androgen metabolism and the menopause. Semin Reprod Endocrinol 1998;16:111–5.
(8)Lobo RA. Androgens in postmenopausal women: production, possible role, and replacement options. Obstet Gynecol Surv 2001;56:361–76.
(9)Vermeulen A. Plasma androgens in women. J Reprod Med 1998;43: 725–33.
(10)Shifren JL, Schiff I. The aging ovary. J Women’s Health Gend Based Med 2000:9 Suppl 1; s3-7.
(11)Judd HL, Judd GE, Lucas WE, Yen SSC. Endocrine function of the post-menopausal ovary: concentration of androgens and estrogens in ovarian and peripheral vein blood. J Clin Endocrinol Metab 1974b;39:1020-4.
(12)Judd HL, Lucas WE, Yen SSC. Effect of oophorectomy on circulating testosterone and androstenedione levels in patients with endometrial cancer. Amer J Obstet Gyn 1974:118(6):793-798.
(13)Simon JA. Androgen levels peak in early adulthood and decrease slowly with aging. Fert Steril. 2002;77:S77-S82.
(14)Janson PO, Janson I. The acute effect of hysterectomy on ovarian blood flow. Amer J Obstet Gyn 1977;127:349.
(15)Reidel H, Lehmann-Willenbrock E, Semm K. Ovarian failure phenomena after hysterectomy. J Reprod Med 1986;31:1597.
(16)Miller KK, Sesmilo G, Schiller A, Schoenfeld D, Burton S, Klibanski A. Androgen deficiency in women with hypopituitarism. J Clin Endocrinal Metab 2001 Feb;82(2):561-567.
(17)Arlt W, Reincke M, Bidlengmaier M. Dehydroepiandrosterone replacement in women with adrenal insufficiency. New Engl J Med 1999;341:1013-1020.
(18)Davis SR. When to suspect androgen deficiency other than at menopause. Fertil Steril 2002;77:68-71.
(19)Geist SH. Androgen therapy in the human female. J Clin Endocrinol 1941;1:154-61.
(20)Gallagher TF, Peterson DH, Dorfman RI, Kenyon A, Koch FC. J Clin Invest 1937;16:695.
(21)Laumann EO, Paik A, Rosen RC. Sexual Dysfunction in the United States: Prevalence and Predictors. J of the American Medical Association 1999;281:537-44.
(22)Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV, 1994).