Sorry, but I just found this site myself, so I just saw your post. While it is not one of the most common side effects, yes...vertigo may be caused by hyperparathyroidism.
The best source of information I have found for this and other parathyroid conditions are as follows: If you have Facebook, look up the "parathyroid disease awareness group." Their website is: www.parathyroid.com
I am curious...have they scheduled surgery for you to remove the tumor on your parathyroid?
I know how crippling both thyroid and parathyroid conditions can be and you have both my sympathy and empathy. Let me know if I can offer anymore help.