We used to discuss this kind of thing before, including even here on PR I think. The usual analogy was in terms of chaos theory, and strange attractors. An attractor is a central point which a system is always tied to, a central tendency about which it revolves, though both those analogies are only half right. If something changes and that attractor is moved, then it shifts to a new stable state. You might push the system a bit, and it will change, but unless the attractor moves to a position that is healthier you have not done anything much...
I was one of the participants in that discussion, and I want to inject a little reminder for those who are not familiar with dynamics. What Alex is describing need not be "chaotic", but it is definitely a problem with dynamics. The dauer state appears to have robust stability, at least in nematodes.
Before we get into a long discussion about changing levels of biochemicals, I want to remind people that levels are the less important part of the metabolic story. Reaction rates are extremely important and different reaction kinetics can lead to the same pathologically-low levels. A low level at one stage may be caused by either inadequate production at an earlier stage, or destruction of the metabolite at that stage, or even consumption at a later stage which increases demand for the biochemical. What is more, every one of the biological pathways revealed by this research involves feedback.
In treatment of depression, where the problem was thought to be low levels of serotonin, simply dumping in precursors to serotonin did not work. This is because metabolic pathways must function with varying diet, and an increase in precursors caused down-regulation of the processes producing serotonin.
What Naviaux has now is a research technique which has grabbed a wide range of metabolites to give us a clue about which pathways are important. This has not told us what we need to know about reaction rates along those pathways, or how these respond to change. I'm not even convinced this is a practical clinical test, due to cost and the difficulty in interpretation. Creating such a test in one go would have been overly ambitious, when so little was known at the start.
Now that we know which pathways are disturbed we can start to fill in the missing information about rates. I expect this to be done, and to yield a whole series of insights. One possibility is to use radioactive tracers, but I think that is still a research method of limited clinical application. This condition is so pervasive that I suspect ordinary harmless chemicals which are easy to detect can be used instead. The rate at which these turn up in blood or urine should give us clues about which reactions are impaired. This has the potential to produce a low-cost clinical test which can tell if a particular pathway is impaired in a particular patient.
As I've said before, about the 2-day cardiopulmonary exercise test, we are not dealing with picograms of material, but with a number of grams of biochemicals which take days to be cleared or replaced.
One more thing, I am less than enthusiastic about provocative tests, following tests in the past which left me wiped out for days, but did not impress doctors. The pervasive nature of this condition lends itself to less drastic means of determining rates without killing patients. As an added benefit, we might just illuminate the problems which lead to adverse responses to particular medications, something all of us have experienced. This has big implications beyond our own group of sufferers. Understanding what is going on in unusual cases might even save lives.