Libido and the Natural Menopause Transition
Professor Lorraine Dennerstein AO MBBS PhD DPM FRANZCP
Professor Dept. Of Psychiatry
Director, Office for Gender and Health
The University of Melbourne
What happens to most women's sexual functioning as they pass through the menopausal transition? Which particular aspects of sexual functioning are affected? Do effects reflect hormonal changes or psychosocial factors such as negative expectations of the menopause? If hormonal factors are involved which hormone is responsible: estradiol or testosterone?
We already know from studies of women attending specialist menopause clinics that sexual problems are amongst the three most common complaints (Sarrel and Whitehead). However women attending such clinics are known to differ from the general population of mid-aged women in a number of ways which limit the results of studies of such convenience groups.
In order to answer the research questions relating to how the natural menopausal transition affects women's sexual response (and other health parameters) I designed a prospective study of mid-aged Melbourne Australian born women in 1990. The project was fortunate in attracting an illustrious multidisciplinary team of co-investigators each with expertise in a different outcome or methodological area of the study. Consequently the Melbourne Women's Midlife Health Project has been able to provide information on how many important health domains change with the menopausal transition.
The study began in 1991 with random digital dialing to find 2,000 Australian born women aged between 45 and 55 years and resident in the Melbourne metropolitan region. A 71% response rate was achieved for eligible women to our request to complete a telephone interview (Dennerstein et al 1993). This baseline cross-sectional study included only three questions on sexual functioning. Nevertheless the results were striking. We found that over 30% of the women reported a decline in sexual functioning and that this decline was significantly linked to the women becoming postmenopausal (Dennerstein et al 1994). Postmenopausal women were also more likely to report a lack of intercourse and to report pain with intercourse (Dennerstein et al 1994).
We then invited those women who were still menstruating and not taking hormone therapies to participate in a longitudinal study which involved annual interviews and hormone sampling in the women's own homes. At the time of the interview each woman was handed a sexuality questionnaire (the Personal Experiences Questionnaire) in an envelope and invited to fill it in and hand it back to the fieldworker in the sealed envelope. The women were followed annually in this manner for 8 years after the baseline telephone interview. Further assessments have been carried out in the 11-13th years of follow-up when the women were postmenopausal but this data has not been fully analyzed.
The study is thus the longest currently running population-based study of the menopause in the world to have included both hormonal measures and validated instruments of sexual functioning and other health parameters. The measure of sexual functioning used was derived from the McCoy Female Sexual Functioning Questionnaire (McCoy and Matyas 1996) and has been extensively subjected to both internal and external validation studies both in Australia and abroad (Dennerstein et al 1997; 2001a; 2002a; Dennerstein and Lehert 2004). We are thus able to now answer the research questions.
What happens to most women's sexual functioning as they pass through the menopausal transition?
We found a major decline in women's sexual functioning as they passed through the menopausal transition. Short Personal Experiences Questionnaire (SPEQ) scores at or below the cutoff score of 7 are indicative of sexual dysfunction (Dennerstein et al 2002a). In the first follow-up year the percentage of women (still menstruating within the last three months) having scores < 7 on the SPEQ was 42%. By the eighth follow-up year the percentage of women (now postmenopausal) with such low scores was 88%. (Dennerstein et al 2002b).
This decline could not be explained by age alone and increasing age also had a significant negative effect on total scores of sexual functioning. (Dennerstein et al 2002b).
Which particular aspects of sexual functioning are affected by the menopausal transition?
The SPEQ measures different domains of female sexual functioning which we have termed Libido (sexual interest), Sexual Responsivity (sexual arousal, enjoyment, orgasm); Dyspareunia (vaginal dryness and dyspareunia); Frequency of Sexual Activities; as well as partner related factors of Feelings for Partner and Partner Problems (in sexual performance) (Dennerstein et al 2001a).
All of these showed substantial changes with the menopausal transition. There was a significant decline in Libido, Sexual Responsivity, and Frequency of Sexual Activities and a significant increase in Dyspareunia as women reached the late menopausal transition (experienced at least 3 months of amenorrhea) and a further decline with postmenopause. Interestingly the women's feelings towards their partner also changed and became less passionate after they entered the late menopausal transition. (Dennerstein et al 2001b).
Do effects reflect hormonal changes or psychosocial factors such as negative expectations of the menopause?
Statistical modeling found that the most important factors influencing mid-aged women's sexual functioning are : her prior level of functioning; any change in partner status (gaining a new partner has a very positive effect while losing a partner has a negative effect on sexual functioning); and her feelings for her partner. These factors explain over 50% of the variance in both Frequency of Sexual Activities and Sexual Response (Dennerstein and Lehert 2004). The findings indicate that women's sexual interest is so tightly correlated to sexual responsivity that it is somewhat artificial to separate these factors. Nevertheless, an important part of the variability remains to be explained.
If hormonal factors are involved which hormone is responsible: estradiol or testosterone?
The late menopausal transition coincides with a steep decline in estradiol but there is no corresponding change occurring in total testosterone (Burger et al 1999; Burger et al 2000). In fact there is a small but significant increase in the free testosterone index at this time due to a decline in SHBG.
We found that this menopause specific decline in sexual functioning was related to the decline in estradiol. Specifically, decline in estradiol affected Sexual Response (sexual interest, arousal, enjoyment, orgasm) and Dyspareunia. There was no significant effect on frequency of sexual activities which in our population seems to reflect factors other than women's own level of sexual interest (Dennerstein et al 2002b).
Clinical implications
As the most important factors affecting mid-aged women's sexual functioning remain her prior level of functioning and relationship factors, these need to be carefully assessed prior to considering the role of hormonal factors. Depression and treatment with antidepressants also need to be excluded because of the known impact on sexual functioning. For women whose decline in sexual functioning is clearly related to the menopausal transition, and where there are no other relationship changes then hormonal factors should be considered.
These findings apply to women passing though the natural menopausal transition. We would consequently expect that replacing estradiol would improve women's sexual interest, arousal enjoyment, orgasmic capacity and vaginal dryness or dyspareunia. However oral estrogens will increase SHBG which will preferentially bind testosterone. Testosterone is already at low levels in the majority of these women. Testosterone is also needed for many domains of female sexual functioning. Replacement of estradiol through the skin is less likely to adversely affect testosterone.
Women who have had hysterectomy and bilateral oophorectomy will have experienced even greater loss of estradiol as well as losing about half the level of testosterone (Judd et al 1974). We would expect that they will experience greater sexual decline than women who experience the natural menopausal transition and surgically menopaused women will have more need for replacement hormones to maintain sexual functioning.
Our project data will be able to supply information on the dose of estradiol needed to restore sexual response. Our preliminary findings are that the current low dose regimes will not be sufficient to restore sexual functioning. The risks /benefits of using hormone therapies must be taken into account when considering the use of hormone therapy for any one woman.
REFERENCES
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Content updated August 2008