NEWS: testosterone alone is not enough to provide for libido

"Testosterone cream fails as sex drive booster" is the title of a Reuters press release that appeared yesterday. An abstract is available from the Journal of the National Cancer Institute, which published it.

The study is a small one and deals with women who are not taking HRT. They found that testosterone cream in a dose of 10mg (!) daily for four weeks did not restore libido despite rising serum levels of the hormone. The press release goes on to say:
It's likely, Barton and her colleagues conclude, that a woman must have adequate levels of estrogen in order for testosterone to be an effective treatment for low libido.
In a related discussion in the editorial section of the Journal of the National Cancer Institute, the authors (of the editorial) note that some 31% of the study participants were taking an aromatase inhibitor, which might also have an effect on total hormone synthesis. While 72% of the participants had an "intact" ovary, ovarian function was not, seemingly, determined. Of sudden menopause, they go on to say,
chemotherapy-induced menopause, which is more abrupt than natural menopause and can have more profound physiologic and psychologic manifestations
This article also reports the results in interesting detail:
The negative results from this study are clearly stated for the primary endpoint of libido (desire/interest) as well as the secondary endpoints of mood, vitality, sexual pleasure, and total sexual functioning. The authors report no statistically significant improvement with treatment compared with placebo for any of these endpoints. Biologic measures that paralleled the questionnaire data from this study revealed statistically significant increases in bioavailable, free, and total testosterone in the treated group, and no changes in serum estrogen, sex hormone–binding globulin, or serum aspartate aminotransferase. These findings suggest that transdermal treatment with 2% testosterone did lead to measurable changes in testosterone levels and that in this short-term study there were no adverse effects on estrogen levels or liver function tests. However, between baseline and 8 weeks of follow-up, both groups showed improvement in almost all the outcome measures, although not differentially by treatment condition, suggesting that there was a large placebo effect in this study sample. Such an effect is consistent with a developing body of neuroscience research on the placebo response, demonstrating direct actions of the placebo on the brain and then subsequent effects on the body such as alleviation of pain or other symptoms.
The authors go on to acknowledge the importance of estrogen in libido, both with respect to vaginal atrophy and in supporting other sensations related to desire. This is exactly the position suggested by the Endocrinologists' Society guidelines (free signup required to read), which also state that estrogen must be brought up to normative levels as the fundamental first step before testosterone can even be reliably evaluated.

Does this conflict with the assertion that in estrogen deficiency testosterone is likely to just be used as an estrogen source? No, that data is fairly clear, as is the risk for women with estrogen-sensitive cancers in taking testosterone. We suspect that in this case the testosterone was simply inadequate to provide that foundation level of estrogen, and so the overall hormone need situation was not especially improved by its use. It's also unclear the extent to which the hormonal therapies for their cancers were affecting both the ability to produce and to synthesize estrogen from other hormones.

What's the takeaway for those of us who are not involved with cancer? I think that the lesson here is clear for all of us in common: testosterone is not a simple remedy for libido loss. I think that this adds to the body of evidence that points to estrogen as the foundation of libido, and that, in practical terms, we must address this deficiency before we can look to adding testosterone as a magic bandaid, however appealing that this may look in simplistic terms.

And, as the editors and authors cited here note, testosterone's risks in women remain very poorly defined. The fact that there is not a lot of information out there pertaining to testosterone's risks for us does not mean that no risks exist, although for both users and physicians who get their health guidance from CNN, that may certainly appear to be the case. The list of "side effects" of licensed testosterone products does not constitute research into total risks, nor do symptom lists constitute an evaluation of the underlying processes. We simply do not have strong, reliable, large-population, controlled research into how testosterone functions in women and what risks go along with its supplementation.

Does all of this mean we are against all use of testosterone? Not at all. But we are, as we are with any hormone or HRT, strongly against use based on simplistic binary criteria with a poor acknowledgment of risks: wishful thinking is not an adequately safe menopausal strategy, and in such highly-loaded stakes as sexual function, we are especially vulnerable to just that danger.

Based on our present, limited state of knowledge, it does make sense that estrogen needs are what we should address as our foundation, and that only after we have seen effective estrogen support to be achieved can we begin to explore other forms of support, one of which may be testosterone. We don't feel that testosterone is "the answer" to libido, although it may be part of the complex factors that contribute to it. And we certainly don't feel that testosterone is "safe" any more than we feel that any hormone, powerful compounds that they are by their very nature, is "safe."