I was pleased to see that the NICE guidelines now state that testosterone therapy is indicated in women. In fact this agrees with guidelines from the British Society for Sexual Medicine, the British Fertility Society, the British Menopause Society, the British Association for Sexual Health and HIV, the British Association of Urological Surgeons, the Royal College of Physicians, the Royal College of Pathologists and the Society for Endocrinology.
Yet most menopausal women who go to their GP complaining of low libido still aren't having their testosterone levels checked or being offered testosterone replacement therapy.
Women need testosterone: lack of testosterone in women can cause low libido, fatigue, lack of motivation, anxiety and depression, weight gain, memory loss, muscle loss, joint aches, and decreased exercise stamina to name a few symptoms. I enjoyed reading the review 'Testosterone in Women – the clinical significance’  which was published in the Lancet in September 2015 and summarises some of the evidence for the vital benefits of testosterone for women, which are as follows:
Nobody would deny that women’s sex drive is a complicated issue!! But large cross-sectional and longitudinal studies have shown that good levels of testosterone and DHEA (an adrenal hormone) improves low sex drive  . Women who are finding it much harder to orgasm or finding that the sensation during sex just doesn't feel the same often respond fantastically to testosterone replacement, because testosterone causes the release of nitric oxide which increases blood flow to the genitals and restores normal function. Testosterone levels can decline with age and there are many other things that can lower testosterone levels in women, namely birth control pills, antidepressants, statins and antihypertensive. Replacing testosterone appropriately can really transform women's sex lives, and there are a number of randomised placebo-controlled trials that support this. .
Testosterone receptors are plentiful in the vagina and testosterone therapy vaginally can help prevent vaginal atrophy. A randomised controlled trial  of 75 postmenopausal women found that vaginal testosterone improved sexual desire, lubrication, satisfaction and pain during intercourse.
Findings from basic studies have shown that oestradiol and testosterone are brain protective. A double blind, randomised, placebo- controlled trial investigated the effects of daily topical testosterone in postmenopausal women aged 55–65: improvements in verbal learning and memory over 6 months were statistically significant. Other well powered observational and interventional studies have shown a link between verbal learning and memory and testosterone replacement therapy given to postmenopausal women.
Not surprising – we know that better levels of testosterone are associated with better hip and lumbar bone densities. The key thing is that when it comes to hormone replacement after the menopause, oestrogen plus testosterone is better for bones than oestrogen alone . This is yet another reason why it is so important to look at replacing all the hormones in balance.
Testosterone levels are directly associated with greater lean body mass in women aged 67–94 years . In a 16 week, double-blind, randomized trial of 40 postmenopausal women, those on oestrogen plus testosterone increased their total lean body mass and reduced their percentage fat for all body parts compared with those on oestrogen alone .
Finally, one paper published in 2015 found that testosterone has a role in decreasing breast cancer risk though much more evidence is needed. 
Many women are afraid that testosterone will make them grow a beard or turn into a man. This is where individualizing the dose is so key: different women have different natural testosterone levels and markedly different sensitivities to testosterone, and treating every individual as just that really reduces the chances of side effects such as hair growth, spots or irritability.