Should I tell my tertiary education provider about my autism and ADHD diagnosis?
If you are in the U.S., and if you are referring to post-high-school education, there is a sort of bifurcation, by law and custom: there's no point in mentioning any sort of trouble unless you have registered with "disability services" (or equivalent), who will negotiate on your behalf with various departments for reasonable/purposeful "accommodation" (about extra time for exams, or quiet rooms for exams, etc)

In that context (again, in current U.S. college or university) individual instructors are explicitly not to make any judgements about disability issues, about accommodations, etc. After all, they/we are not experts in understanding such things.

Similarly, (other) chronic medical conditions (since the previous is biochemistry, presumably) are not within the purview of instructors. E.g., the side effects of anorexia or bulimia can be occasionally debilitating. Despite being able to make inferences, I do not want to intrude in peoples' private lives, so I do not ask for any sort of detailed explanation for anything. "Medical issue" (as reason for absence or "incomplete") is more than enough.

It is unfortunately true that the "immediacy" of most classroom/exam situations (such as demands for "class participation") are biased against shy or nervous or ... people. The typical rationalization for this is that it is often unhelpful "out in the world" to be shy or nervous or ... so to operate in a way that penalizes that is merely a presagement of what is to come? (Um, wait, don't people pay tuition, not to be filtered only, but to be educated and assisted in that education? Nevermind.)

You might make a more informal remark, as pseudo-apology-in-advance, explaining possibly unusual behavior or reactions as due to ... whatever you'd care to say... rather than a negative-critical reaction to whatever's happening in class. But something more on the order of "I have some personal issues that may cause me to behave quirkily at some points, and I don't want you (the instructor) to think that it's at all a reaction against what's going on, it's just me". Or to your taste. No reason to give more details to any reasonably sophisticated college/university instructor in the U.S. (Of course, some are not sophisticated, and further, often themselves having issues that make such sophistication difficult, sadly-ironically.)

A bit ambiguous answer, but reflecting the legalities and intentions of current U.S. stuff, I think.