Sexual desire in both men and women is primarily a biological phenomenon governed by sex hormones, neurotransmitters, and the vascular and neurological systems that support sexual function. The widespread attribution of midlife libido decline to psychological factors, relationship habituation, or stress, while not without some basis, has led to underinvestigation and undertreatment of what are in many cases clearly hormonal presentations. The endocrinology of sexual desire is well characterised, and the clinical response to it is increasingly evidence-based.
Testosterone and Female Libido
Testosterone is the primary androgen responsible for sexual desire in women as well as men, though this fact is poorly communicated in clinical practice. Testosterone in women is produced by the ovaries and adrenal glands and acts on androgen receptors in the brain, genitalia, and other tissues. It peaks in the mid-20s and declines progressively thereafter. By the perimenopause, testosterone levels have fallen to approximately half their peak, and this decline produces measurable reductions in sexual interest, fantasy, and responsiveness in a significant proportion of women. Hypoactive sexual desire disorder in women is the most common female sexual dysfunction and has a substantial hormonal component in most cases.
Testosterone and Male Libido
In men, testosterone declines at approximately 1 to 2 percent per year from around age 30, producing a cumulative 40 to 50 percent reduction by age 70 in most cases. The relationship between testosterone and libido in men is dose-dependent at low-normal and below-normal concentrations but plateaus above a threshold of approximately 10 to 12 nanomoles per litre. Men with serum testosterone below this threshold consistently show reduced libido, lower sexual activity, depressed mood, and reduced energy. Testosterone replacement therapy in hypogonadal men restores libido in the majority of cases, with evidence from multiple randomised controlled trials.
Oestrogen and Sexual Function
Oestrogen deficiency in postmenopausal women produces genitourinary syndrome of menopause, formerly called vulvovaginal atrophy, which includes vaginal dryness, reduced lubrication, pain with intercourse, and reduced genital sensitivity. These physical changes independently reduce sexual desire and frequency through both discomfort avoidance and altered neurological sensitivity in genital tissue. Local oestrogen therapy, applied directly to the vaginal tissue, is highly effective for genitourinary syndrome and is not absorbed systemically in meaningful quantities, making it safe for use in women who cannot or choose not to use systemic HRT.
- Discuss testosterone testing with your GP if you have reduced libido alongside fatigue, low mood, or reduced physical energy
- For postmenopausal women with vaginal dryness and pain: local oestrogen therapy is safe and highly effective
- Lifestyle factors that support healthy testosterone: resistance training, adequate sleep, healthy body weight, stress reduction, and reduced alcohol
- Do not accept libido decline as an inevitable consequence of age without hormone investigation: treatable causes are common
- For women: testosterone therapy is not currently licensed for libido in the UK but is available off-label and endorsed by NICE for hypoactive sexual desire disorder
Sources
- Davis, S.R., et al. (2019). Global consensus position statement on the use of testosterone therapy for women. Journal of Clinical Endocrinology and Metabolism, 104(10), 4660-4666.
- Isidori, A.M., et al. (2005). Effects of testosterone on body composition, bone metabolism and serum lipid profile in middle-aged men. Clinical Endocrinology, 63(3), 280-293.