First, I am not an Endocrinologist. I am but a lowly GP who broke away from conventional medical training to concentrate full time on manipulating hormone levels in male patients. The trip to the cutting edge went much faster that way.
The plain truth is we do not know why this happens. But it is consistently reported too many times to ignore.
And you do not have to go anywhere near that high in dosing to achieve the same bad result. I have had quite a few patients come in (perhaps "treated" by some online "HRT Clinic") with androgen levels, say, twice the top of normal range. I bring them back down to the upper quartile. They tend to squawk a bit at first, but once their T levels are nestled within that upper quartile, their libido comes right back. And it tends to stay that way! They also report they just feel much better. That is another reason why appropriate TRT ONLY goes to the top of normal range.
Everyone who has supplemented testosterone--whether as AAS or TRT--will tell you that AT FIRST all they wanted to was to follow their penis around all day. This is because when serum androgen levels are accelerating, libido rockets as well. And while it is dropping--even when dropping to the top of normal range--libido falls away, too. Then it re-equilibrates.
I'd also have to ask whether estrogen is being controlled. It can flatten sexual function, too. That is one reason why it must always be controlled, I prefer to keep it near midrange. The best reason for doing that, though, is that elevated estrogen levels are very bad for your health.
