Testosterone: A Hormone Beyond Gender

Exploring Its Role in Male and Female Health

Testosterone, a key androgen hormone, is well-known for its role in male health, contributing to physical attributes such as muscle mass, bone density, and the regulation of libido. Yet, in recent years, the use of testosterone has gained attention not only in men but also in women, particularly those undergoing menopause. This shift is supported by emerging research that highlights its broader physiological roles and potential therapeutic applications.

Testosterone in Men

In men, testosterone is primarily produced in the testes and is responsible for a variety of functions, including the development of male reproductive tissues, maintenance of secondary sexual characteristics, and influence on mood and energy levels. Low testosterone, commonly termed as “low T,” can lead to a range of symptoms such as decreased libido, fatigue, loss of muscle mass, and mood disturbances.

Mechanistically, testosterone acts through binding to androgen receptors present in various tissues, including muscles, bones, and the brain. This binding initiates a cascade of gene expression changes that promote anabolic effects, enhancing protein synthesis and leading to increased muscle strength and growth. Moreover, in the central nervous system, testosterone modulates neurotransmitter systems, contributing to its influence on mood and cognitive function.

Testosterone Use in Men: The Research

A comprehensive meta-analysis published in the Journal of Clinical Endocrinology & Metabolism (2016) reviewed the effects of testosterone replacement therapy (TRT) in men with hypogonadism. It concluded that TRT can significantly improve sexual function, muscle mass, and bone density. However, it also noted potential cardiovascular risks, highlighting the need for individualised treatment plans.

Diagnosing Low Testosterone in Men

According to guidelines, diagnosing symptomatic testosterone deficiency (TD) in men requires the presence of characteristic signs and symptoms (such as reduced libido, fatigue, and muscle weakness), combined with decreased serum concentrations of total testosterone (TT) or free testosterone (FT) levels (Lunenfeld et al., 2015). This diagnostic approach ensures that treatment is targeted to those who are both symptomatic and biochemically confirmed to have low testosterone, reducing the risk of overdiagnosis and overtreatment.

Despite these benefits, the long-term safety of TRT remains controversial. Studies have shown mixed results, with some research suggesting increased risks of cardiovascular events, while others indicate neutral or even protective effects. As such, clinical guidelines recommend that TRT should be considered only when symptoms significantly impair quality of life and after thorough evaluation.

Testosterone in Women

For women, testosterone is produced in smaller quantities by the ovaries and adrenal glands and has historically been overlooked in female health. However, testosterone levels decline with age and drop significantly after menopause, which has prompted researchers to investigate its potential therapeutic role in this population.

Testosterone is known to contribute to libido, energy levels, and overall well-being in women. A landmark study in The Lancet Diabetes & Endocrinology (2019) found that testosterone therapy in postmenopausal women can enhance sexual function, particularly in those experiencing hypoactive sexual desire disorder (HSDD). The study noted improvements in sexual satisfaction and arousal without significant adverse effects at physiological doses.

Mechanisms of Testosterone in Women

In women, testosterone works through similar androgen receptors as in men, influencing tissue growth, sexual health, and mood. In the brain, testosterone increases dopamine levels, which may partly explain its role in enhancing libido. Additionally, the hormone modulates serotonin activity, contributing to its impact on mood and cognitive function.

Guidelines for Monitoring Testosterone Therapy

Before starting testosterone therapy, it’s essential to check baseline levels to understand the individual’s starting point and ensure they are not already at the high end of the normal range. This initial measurement helps guide treatment decisions and future monitoring. The most accurate method for measuring testosterone is using liquid or gas chromatography combined with tandem mass spectrometry. However, simpler direct assays are often employed in clinical settings (a visit to your GP) to rule out abnormally high levels before therapy begins and to monitor for excessively high concentrations during treatment.

Current guidelines recommend reassessing testosterone levels 3-6 weeks after initiating treatment. However, due to practical constraints, most NHS clinics review patients within 2-3 months. Regular monitoring should then continue every 6-12 months to ensure that testosterone levels remain within the physiological range for women, reducing the risk of potential adverse effects such as virilisation (e.g., increased body hair, deepening of the voice) and metabolic changes. It is crucial that these checks are maintained throughout the duration of the therapy to ensure safe and effective treatment.

Potential Risks and Considerations

Despite the potential benefits, there are concerns regarding long-term safety, particularly in women. Higher-than-physiological doses can lead to virilisation and adverse metabolic changes. Thus, current guidelines from the International Menopause Society suggest that testosterone should only be used in women with a definitive diagnosis of HSDD and under careful clinical supervision.

So what can we take from this?

The therapeutic use of testosterone for both men and menopausal women is a complex and evolving field. While research supports its benefits in terms of sexual health, mood, and physical function, concerns regarding long-term safety remain. As such, clinicians and patients must work together to weigh the potential benefits against risks, tailoring interventions to the individual’s unique health profile.

Further research is needed to establish definitive safety profiles and optimise dosing strategies, ensuring that testosterone therapy can be used effectively and safely across different populations.