What are the consequences bodybuilding training and testicular exhaustion?

The answer to the paradox of having a strong LH elevation and negative testosterone response is easy. The testes of these advanced athletes are “exhausted”. Their constant stimulation ends up having a very negative contact on their capacity to manufacture androgen's.
In this study, this exhaustion occurred after only 8 years of training. Basal testosterone is not affected, yet. Subjects were still pretty young (25 year old), too. With more training years and as you get older, basal testosterone production is likely to suffer, too. Think this exhaustion explains why so many advanced (natural) bodybuilders end up having short levels of androgens or end up producing no testosterone at all.

Note that the free (bio-available) testosterone is the most affected in both groups. It increased the most in the least experienced athletes compared to total testosterone. It decreased the most in the elite assembly. In that, it resembles to an accelerated configuration of aging. As we age, the producing of the proteins that bind testosterone increases 1% every year. If our testosterone output decline yearly, our free segment is the most negatively affected.

The ‘testicular exhaustion’ is a factor one should take into account when planning his bodybuilding career. When you thing about it, the future does not look very bright. Up to the lifetime of 25, athletes could tell that a workout, especially a leg workout, was increasing my testosterone level. More than 10 years later, such a feelable kick is very, very rare. Unless you want to become a pro bodybuilders,  not recommend starting using steroids before reaching this exhaustion stage.
Low calorie diets are obviously not a correct thing for your testosterone output. Overfeeding is not a very strong stimulator for your testosterone producing. On the other hand, underfeeding is a potent inhibitor of testosterone output. After several years of bulking up, a severe diet might precipitate this testes exhaustion.
The new rationality of the aging bodybuilder: Statistical studies suggest that muscles can still increase despite a low testosterone output. In fact, muscles growth is more closely related to testosterone receptor density than testosterone level. This indirect finding suggests that testosterone receptors can self activate in the absence of testosterone if powerful contractions are intense enough. But in extreme case of exhaustion, testosterone replacement remedy (TRT) might be the only solution.