Androgens in Health and Disease.pdf - E Library

Chapter 14/Androgens and Sexual Function 273
Reported decline in sexual interest was associated positively with body weight but was
unrelated to androgen levels. However, in each of these studies, the youngest women had
presumably already reached the premenopausal T decline, and to adequately test the
hormone–behavior relationship, the age range should include women before this developmental
stage.
In the only longitudinal behavioral study of women in transition through the menopause
so far published, McCoy and Davidson (93) found correlations between declining
levels of T and coital frequency. However, only 16 women continued in this study (23
of the original 39 dropping out because they wanted hormone-replacement therapy
[HRT]) and this number did not allow adequate multivariate analysis. The behavioral
results of the much larger longitudinal study by the Melbourne group (84) are awaited
with considerable interest.
HORMONE REPLACEMENT AND THE NATURAL AND SURGICAL MENOPAUSE
In spite of the above reviewed evidence, it is still often assumed that the menopause
is associated with a decline in testosterone and that this fact is itself justification for using
T in hormone replacement. It is of crucial importance to make the distinction between
natural and surgical menopause. As already discussed, the evidence indicates that reduction
of T in women occurs in the years before the natural menopause and that T levels,
although variable across women, show no predictable change thereafter. With surgical
removal of the ovaries, there is an immediate and substantial drop in circulating androgens.
There are, however, other reasons for considering T replacement in HRT regimes
for the natural menopause. The administration of exogenous estrogen in HRT increases
SHBG and, consequently, reduces free T. Conversely, T administration will reduce
SHBG levels and also, because of competitive binding with SHBG, increase the amount
of free E2. However, in evaluating the literature on T replacement with naturally or
surgically menopausal women, a number of factors need to be taken into consideration.
1. Improvement in sexual interest or enjoyment may be secondary to more general improvement
in well-being, mood, and energy. In a study of variations in mood and sexual interest
through the menstrual cycle of young women, Sanders et al. (94) found that around onethird
of the variability in sexual interest could be attributed to a more general variability
in well-being. Cawood and Bancroft (89) found, in women aged 40–60 yr, that measures
of mood and energy were the best predictors of sexual well-being, and this association
has been strongly replicated in the recent Kinsey national survey of women, aged 20–65,
referred to earlier (88a).
2. Improvement in sexual interest and enjoyment may be secondary to improvement in
vaginal dryness and associated dyspareunia, which can have negative repercussions on
women’s sexual enjoyment and, consequently, sexual interest.
3. Improvement in mood and well-being and, consequently, sexual interest associated with
T administration may result from the effects of the exogenous T in increasing free E,
rather than from direct T effects. Such an increase results from aromatization of T to E
in the tissues, as well as preferential binding by T to SHBG. Although there is still
uncertainty about the precise physiological role of steroid binding in influencing the
relative impact of E and T (95), this mechanism of using exogenous T to increase free E
has been strongly advocated by Wallen and supported by experimental data from rhesus
monkeys (96). For these various reasons, it is not possible to establish whether improvement
produced by a combined E + T regime is the result of the E, the T, or a combination
of the two.