Interesting, I am not in a study, but have many many blood tests. Like you, one just came back also with elevated cortisol and sex binding globulin! I was going to ask my Gynecologist what sex binding Globulin is. The study results that just came out in the news said more people in the study with long Covid had LOW cortisol, explaining the fatigue. But I have unbelievable fatigue with HIGH cortisol. One of my friends a nurse said that overly high cortisol can make you tired too, because it exhausts your body being in fight of flight mode much of the time, induced by high cortisol.
I'm going to ask one of my many doctors I have now to re do my covid immunity test of a year ago when my immunity read really high, also want the Epstein Barr Antibody test, both also markers more people with long covid in the study had. At least if we had a number of the markers it would show we have something provably going on. I also had some other tests showing possible autoimmune diseases if you have a positive on those. Almost 2 years for me now,! I have cardiac Arrhythmia, terrible GI symptoms, chronic fatigue, now have nerve symptoms that came after I had my thyroid removed which my cardiologist and Endocrinologist agreed would at minimum fix my thyroid problem and get rid of my heart arrhythmia, but NO it did not, and now I also have the nerve symptoms in addition. Miracle you got in study, I tried but I didn't have a positive PCR test so was rejected, so much for using the recommended home tests!