Testosterone vs Male Sexual Fxn: When Is Enough Enough?

So while we're on the subject of testosterone, just how much do we really need?  Well, it appears that more is better at least when it comes to all-cause and cardiovascular mortality.  However, that relationship seems to be rather linear.  In other words, there's no point of diminishing return at which one says "enough".

But what about sexual function?  Is there a minimum level that serves as a cut-off for sexual function in men?  In a study published this month, the authors concluded that sexual function improves up to a testosterone level of 230ng/dL (8nmol/L), over which said performance plateaus.  In other words, any testosterone more than 230ng/dL is wasted, at least as far as sexual performance goes.

The authors arrived at their conclusion by taking a self-reported validated sexual function survey of 2,838 European men average 60yo and comparing their answers to various sex hormones.  Of note, these men from 8 different countries had to have a current sexual partner, could not have a pituitary or testicular disease, and could not be taking any medication that might affect pituitary or testicular function or sex hormone metabolism.

More specifically, the authors noted that testosterone was related to self-reported sexual function but only up to 230ng/dL after which there was no further association/improvement.  In other words, there exists a threshold above which there is no need for more.  Of course, this study did not intend to study testosterone's association w/mortality which explains the low level necessary for erectile function and sexual satisfaction (as opposed to higher levels for other endpoints).  Interestingly, estradiol was associated w/sexual distress, which is why it's important to check the metabolic byproducts of testosterone in addition to testosterone levels.

Given these findings, it makes sense that the manufacturers of Androderm are only aiming for a total testosterone level of 300ng/dL.  However, in light of observational and epidemiological data, I think that we need a randomized, double-blind, placebo-controlled study whereby participants are treated to a clinical endpoint, not just a numerical goal.  But hey, that's just me thinking outloud.

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