This is a large-scale study comparing the testosterone therapy (TT) group vs the PDE5i group.

Although the myocardial infarction risk is raised in the TT group, but the results have to be interpreted with caution, simply because the cohorts being studied may have totally different baseline condition which may interfere with the results.

As the article has pointed out, "Testosterone therapy has been used in healthy older men to treat diminished strength and physical function associated an age-related decline in serum testosterone", patients in the TT group usually have confirmed low level of testosterone level before any replacement is given, i.e. they have low testosterone level to start off with.

On the other hand, the PDE5i group involved patients presented with erectile dysfunction. The cause of erectile dysfunction in the vast majority will be vascular-related rather than hormonal-related. Even if these patients really have low level of testosterone, then the treatment should involve testosterone replacement rather than PDE5i. I think it would be logical to think that the majority of the patients in the PDE5i group have normal testosterone level to start off with, if not all of them.

If we look into the literature about the effect of testosterone on myocardial infarction, one of the big areas will be the use of androgen deprivation therapy (ADT) in the treatment of prostate cancer. ADT either in the form of bilateral orchiectomy or gonadotrophin releasing hormone analogue reduces the testosterone level into a castration level. And it has been shown by many studies that this will increase the risk of diabetes, myocardial infarction and stroke. It would therefore be quite unfair to comment that the use of TT will increase the risk of myocardial infarction, given the fact that all these patients have low testosterone level to start off with, which means that they are already predisposed to the risk of myocardial infarction even before starting the treatment. On the other hand, in the PDE5i group, since the majority of the cause of erectile dysfunction is vascular-related, these patients are also predisposed to myocardial infarction. This makes the comparison between the TT group and the PDE5i group even more complicated.

Although this is a large-scale study with significant findings, I would say that the results have to be interpreted with caution and further studies on the effect of testosterone on myocardial infarction will be needed.