What could cause my period to disappear?

It's called a metabolomics. But metabolomics is a way to kind of do a deep dive to see what's happening with your chemistry dynamically and a lot more data than a typical blood test. But if you get a hormone test just to find out what's going on, maybe you need to tweak what what you're eating because if you're doing the healthy version of the ketogenic diet and getting all your nutrients, you shouldn't have that problem. I would make sure that the foods are nutrient dense. I can't evaluate fully without knowing what you're eating.