Lesser known causes of low T?

I started on TRT about 8 years ago for low T, and I have always questioned why I can’t produce my own. In the last several years I’ve had testicular ultrasound, brain mri, sleep study, tons of labs. For a brief period late last year I felt better when taking zinc. I had my levels checked then and with one single total T value of 350 I was discharged from endocrinology. Now I’m feeling like crap again and just tested at 240. I’m ready to give in and beg for TRT again, but I’m curious if there are other more obscure causes that I should look into first. Thanks for your thoughts.