You are not alone. While very low T can cause impotence, few of those diagnosed with impotence and treated with PDE5 inhibitors are impotent due to low T. If one ignores the possibility that one's T was normal and that supplemental T merely downregulated natural production, then T was not low enough to be the cause. Here is some info from a couple of recent studies.
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Testosterone added to sildenafil ( Viagra, Pfizer) is no better than placebo in improving erectile dysfunction (ED) or sexual satisfaction, according to a study published online November 19 in the Annals of Internal Medicine.
Many men with ED also have low testosterone. ...
"The primary analysis indicated that 14-week change in EFD score after randomization...did not differ significantly between the testosterone and placebo groups (difference between mean changes, 2.2 [(confidence interval), −0.8 to 5.1]; P = 0.150)," the researchers conclude.
Secondary outcomes also did not differ between the 2 groups. Frequency of attempts at sex, vaginal penetration, ejaculation, satisfaction, and percentage of successful encounters improved to similar degrees in both groups, indicating that sildenafil was responsible for the improvements, and not testosterone supplementation. Frequency of adverse events also did not differ between the testosterone and placebo groups.
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"The bottom line is that addition of testosterone adds to PDE5 only in men who have very low testosterone levels. The men in the current study did not have these low levels," H. Ballentine Carter, MD, professor of urology and oncology at Johns Hopkins Medicine in Baltimore, Maryland, told Medscape Medical News. He pointed to a study finding a similar lack of effect of supplementary testosterone in men taking tadalafil ( Cialis, Lilly) ( J Sexual Med. 2011:8:284-293). Dr. Carter was not involved in the current study.
