Is testosterone important for women?

Testosterone is the most biologically active hormone in women's blood, present in higher concentrations than oestradiol. It acts partly directly in tissues and is partly converted to oestradiol. Although it is considered essential for physical and mental health, scientific evidence about its precise mechanisms and the consequences of a deficiency in women is still limited.

The strongest clinical evidence concerns sexual desire. In postmenopausal women with low sexual desire (medically referred to as HSDD), a large meta-analysis of 36 randomised trials with more than 8,400 participants shows that transdermal testosterone increases the number of satisfying sexual experiences, improves desire and arousal, and reduces sexual distress. The effect is real but modest: on average just under one additional satisfying sexual experience per month compared with placebo.

On the safety side, the findings are nuanced. Transdermal testosterone (applied through the skin) at doses normal for women produces no serious adverse effects in the available studies, but acne and increased body hair occurred more frequently than with placebo. Oral testosterone is a different matter: that route of administration raises LDL cholesterol and lowers HDL cholesterol, which is unfavourable for the heart. Oral testosterone is therefore not recommended. Compounded preparations from unregistered providers lack evidence for both efficacy and safety and cannot be recommended either.

What testosterone does not do in women is at least as informative. Current data do not support a role for testosterone in improving bone health, energy or cognition. The studies in these areas are too small and too scarce to draw conclusions. There are some preliminary signals that transdermal testosterone may alleviate mood and cognitive complaints during menopause, but these rest on a single retrospective study without a control group: randomised trials for this indication are still lacking.

A crucial caveat is long-term safety: that has simply not yet been established. There are no approved testosterone preparations for women in most countries worldwide, precisely because of the absence of long-term data on cardiovascular disease and cancer. This makes testosterone therapy in women something that should only be considered in consultation with a doctor, with a clear indication (such as diagnosed HSDD) and preferably via the transdermal route. At the other end of the spectrum, too much testosterone, as seen in PCOS, causes clear symptoms such as excessive hair growth. Measuring testosterone is useful in that context, although commercially available tests are not always accurate.