I was diagnosed with OP when I was 54yo and there wasn't any good explanation. The reason my primary doc would give is I was Northern European descent; yeah lame. Anyway, after a lot of moaning and groaning to various docs one sent me to a rheumy who ran a bunch of tests. When I saw him he asked if I had ever had any stomach problems. I have a cast iron stomach I could eat anything. So he said I have Celiac and the only symptom is OP. I knew one person whose only symptom was anemia. Celiac has a very wide variety of symptoms; aren't we lucky!
I follow the GF diet 100% and really don't have any problems with that. It's just a life style you adjust.