Testosterone, because of its libido connection, helps men achieve an erection. (tctmed.com)
These include, but are not limited to the correct temperature range in the testicles, the male's ability to achieve an erection sufficient for sexual intercourse, an ample supply of key nutrients to provide the building blocks for the spermatozoa during the process of spermatogenesis, the correct hormone balance such as plenty of testosterone and few stress hormones as well as little exposure to environmental toxins and potent antioxidants to combat oxidative stress. (aminoacidstudies.org)
In men with low testosterone levels achieving an erection may take much longer than it once did. (tctmed.com)