Erectile dysfunction

What it is

Erection is a chain that starts with sexual stimulation. Stimulation releases NO, which drives an enzyme pathway from GTP to cGMP, and cGMP widens the vessels and gives the erection; in the erect state the expanded sinuses compress the subtunical venous plexus under the tunica albuginea. PDE5 breaks down cGMP, and that is the step where sildenafil acts. Erectile dysfunction is the loss of that erection, and the treatment options are built on the same pathway.

Causes and risk

Common drugs point straight at it. The 5 alfa reductase inhibitors given for BPH cause erectile dysfunction in about 10%, and they also lower the PSA level, so PSA is measured before they are prescribed. The alfa 1 blockers, also used for BPH, cause a different problem, postural hypotension and ejaculatory dysfunction with retrograde ejaculation, and that is not the same thing as erectile dysfunction. Curative treatment of prostate cancer carries urinary incontinence and erectile dysfunction, which is one of the harms weighed against PSA screening, together with overdiagnosis of tumors that are not life threatening, overtreatment of them, false-positive and false-negative results, and the complications of biopsy. Compression of the cord counts too: erectile dysfunction is listed among the urogenital symptoms of conus medullaris syndrome and of cauda equina syndrome. Hypogonadism belongs on the list too, since testosterone supplements are given when it is present.

Hypogonadism is ruled out by hormonal evaluation, and the four tests that make it up are named: luteinizing hormone, testosterone, free testosterone and prolactin. That set is what is sent before the phosphodiesterase type 5 inhibitors, because a low testosterone is treated as its own problem.