What are the implications of low normal range testosterone levels and elevated estrogen levels in a male?

From the Research

Implications of Low Normal Range Testosterone Levels

• Low testosterone levels have been associated with an increased risk of cardiovascular disease (CVD) and mortality 1
• Testosterone deficiency can have an adverse effect on several cardiovascular risk factors, including insulin resistance, diabetes, dyslipidaemia, central adiposity, and endothelial dysfunction 1
• Men with endogenous testosterone levels in the mid-upper normal range have reduced cardiovascular events and mortality compared to those with low or lower range, and with high range testosterone 1

Implications of Elevated Estrogen Levels

• Elevated estrogen levels in men can increase the incidence of erectile dysfunction independently of low testosterone levels 2
• Estrogen plays a critical role in male sexual function, including modulating libido, erectile function, and spermatogenesis 2
• High estrogen levels have been observed in men after injectable testosterone therapy, with approximately 20% of patients having high estradiol levels 3

Interaction between Testosterone and Estrogen

• The balance between testosterone and estrogen is controlled by gonadal secretion and peripheral conversion by aromatase 4
• A testosterone:estradiol ratio between 10 and 30 appears to be associated with improved spermatogenesis and reduced bone density, while lower values are associated with thyroid dysfunction 4
• The optimal testosterone:estradiol ratio has not yet been determined, and further work is needed to clarify the measurement strategies and clearly-defined outcome measures related to this ratio 4

Clinical Implications

• Testosterone replacement therapy can have a beneficial effect on several cardiovascular risk factors, cardiac ischaemia, functional exercise capacity, and improved mortality, but clinical monitoring and titration of testosterone dose is of paramount importance 1
• The treatment of elevated estrogen levels during testosterone replacement therapy is not well established, and further research is needed to determine the clinical implications of high estrogen levels in men 5, 3