I agree. Ultrasounds, even the sestamibi scans will usually NOT show a parathyroid tumor... the sestamibi scan is often done incorrectly according to reading I've done. Honestly if you have a huge lump in your neck and your doctor says your blood work is off, why aren't they bringing up the possibility of you have hyperparathyroidism?
Endocrinologists are often not used to dealing with cases like this so many will be ignorant about it and write it off as something else. DO NOT GIVE UP! I was in the same boat as you where I was told I had Arthritis or fibro but I knew I was right... now new labs have shown results that I really might have this disease too. Lab work is key in getting diagnosed. NOT scans. Good luck with everything.