Testosterone Deficiency and Endothelial Dysfunction: Nitric Oxide, Asymmetric Dimethylarginine, and Endothelial Progenitor Cells

INTRODUCTION: Testosterone deficiency is known to induce endothelial dysfunction, which can lead to erectile dysfunction and/or vascular dysfunction. In some basic and clinical reports, testosterone has been shown to regulate the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway and thereby influence endothelial function and endothelial progenitor cells (EPCs), which are key for the endothelial repair system. AIM: To review the association between testosterone and endothelial dysfunction focusing on NO and EPCs. METHODS: A review of relevant literature up to September 2018 was performed via PubMed. MAIN OUTCOME MEASURES: We reviewed the association between testosterone and endothelial dysfunction focusing on NO derived from endothelial NO synthase, phosphodiesterase type 5 (PDE-5), asymmetric dimethylarginine (ADMA), inflammation, and EPCs. RESULTS: Numerous articles describing the association between testosterone deficiency and endothelial dysfunction have been published. Some reports have shown that testosterone deficiency decreases NO production by altering the expression and activity of NO synthase and by regulating ADMA expression. Testosterone also regulates the expression of phosphodiesterase type 5. In addition, some basic and clinical studies have shown that testosterone affects the function and number of EPCs. However, some inconsistencies among these reports have been noted. CONCLUSION: Testosterone deficiency might cause endothelial dysfunction by decreasing NO levels through regulating the expression and activity of NO synthase and increasing ADMA expression. In addition, testosterone might affect the endothelial repair system by regulating the proliferation and migration of EPCs. Testosterone replacement therapy might be useful for treating endothelial dysfunction, considering that some reports have shown that this therapy improved NO bioavailability and EPC function. Hotta Y, Kataoka T, Kimura K. Testosterone Deficiency and Endothelial Dysfunction: Nitric Oxide, Asymmetric Dimethylarginine, and Endothelial Progenitor Cells. Sex Med Rev 2019;7:661-668.