Acute endothelial response to testosterone gel administration in men with severe hypogonadism and its relationship to androgen receptor polymorphism: a pilot study

PURPOSE: Testosterone (T) exerts different effects on the cardiovascular system. Despite this knowledge, the acute vascular effect of androgen remains still poorly understood. METHODS: We investigated the acute effects of T on vascular function in ten men (18–40 years age) with hypogonadism and severe hypotestosteronemia [serum total testosterone (TT) = 0.6 ± 0.3 ng/mL]. In a 4-day double-blind, randomized, placebo-controlled crossover study, we administered 80 mg daily dose of transdermal-T gel (TG) and evaluated endothelial variations with Endopat2000 (reactive hyperemia index, RHI and the augmentation index, AI); also, CAG repeat polymorphism in exon 1 of the androgen receptor gene was investigated. RESULTS: After TG administration, RHI significantly improved at 4 h (p < 0.05), while AI improvement was recorded at 4 and 96 h, also when adjusted for heart rate (AI@75; p < 0.01 and p < 0.001, respectively). Direct relationships between ΔT, ΔDHT and ΔRHI variations (r = 0.37, p < 0.01; r = 0.17, p < 0.05, respectively) as well as between “CAG repeats” length and ΔLnRHI at 96 h (p < 0.03, r(2) = 0.47) were found. An inverse relationship between ΔT and ΔAI (p < 0.01, r = −0.35) and ΔAI@75 (p < 0.01, r = −0.38) were found. CONCLUSION: Administration of TG causes an acute vasodilation and improves arterial stiffness probably due to non-genomic actions of T. Endothelial vasodilatory response was more pronounced depending on higher plasma TT and DHT levels attained. Clinical implications in elderly frail populations are discussed.