Objective: The vascular effects of fluctuations in testosterone levels within the physiological range in otherwise healthy men are not known. We therefore aimed to study arterial function in hypogonadal men receiving long-term physiological androgen replacement therapy, at trough and peak testosterone levels.
Patients and design: We recruited nine hypogonadal men (aged 35 +/- 4 years) receiving androgen replacement therapy, each treated with 800 mg testosterone (T) depot preparations every 6 months.
Measurements: Serum lipid and hormone levels and arterial reactivity were measured, prior to (trough T) and 2-4 weeks following testosterone administration (peak T). Each subject therefore served as their own control. Vessel diameter was measured by ultrasound at rest, during reactive hyperaemia [leading to flow-mediated dilatation (FMD), an endothelium-dependent response] and after sublingual nitroglycerin (GTN, an endothelium-independent dilator).
Results: Serum T (13 +/- 2 nmvs. 27 +/- 3 nm for trough and peak serum T, respectively, P < 0.001; normal adult male range 11-35 nm), and free T (195 +/- 23 pmvs. 510 +/- 93 pm, P < 0.005) significantly increased following subcutaneous depot T administration, as did serum oestradiol (100 +/- 10 pmvs. 175 +/- 9 pm, P = 0.001; normal adult male range < 250 pm). There was a significant decrease in FMD (3.6 +/- 1.1%vs. 3.0 +/- 0.8%, P < 0.01), but GTN responses were similar (9.5 +/- 0.8%vs. 10.4 +/- 1.0%, P > 0.2). Lipid, blood pressure and vessel diameter measurements were also similar before and after testosterone administration.
Conclusion: Physiological replacement of testosterone is associated with decreased endothelium-dependent dilatation, in hypogonadal men.