I have TINU Syndrome (affects eyes through iritis and low kidney function - helped with oral steroids) that was discovered through a kidney doctor. My iritis began one morning in early January 2010 and the ophthalmologist put me on a dilator drop and topical steroid drops. After several rounds of inflammations in both eyes, he sent me to a gen practitioner, who ran some blood work recommended by the eye doc, and I also asked for a physical to rule out anything else. Most all came back negative, except my kidney functions tests. After a few more tests with the general practitioner, I went to a kidney doctor who ran more tests on my blood and urine. When those came back negative she had me get a kidney biopsy at the local hospital. Based on the biopsy results, she diagnosed me with TINU syndrome. From initial symptoms to diagnosis was six months for me. No one knows what causes TINU syndrome, but they know how to find it and how to treat it. I'm doing well so far as my kidneys are almost back to normal and it's been several weeks since my last iritis flare.
Symptoms I had prior to being diagnosed, that are indicative of TINU syndrome, are loss of appetite, weight loss (15 lbs for me over several weeks without trying), weakness, fatigue, and iritis in one or both eyes (bilateral). (Of course, looking back at what when I had these symptoms, I didn't know they were related to the TINU, but putting the pieces together I realize that is what I was experiencing.)
For you, I would suggest going to a general practitioner and have them run a physical on you to rule out anything. I'm no doctor, just sharing my experiences, but it worked for me. Hopefully it will help you to find out what might be going on there.