What Causes A Sudden Flip From Hypothyroid To Hyperthyroid?

I have been borderline Hypothyroid for many years and Hashimoto s with a nodule on my Thyroid that is too small to biopsy but, yearly ultrasound are done to monitor changes...I just found out my Triglycerides plummeted and also flipped to Hyperthyroid...no medication has ever been taken for this to overcorrect. I have Fibromyalgia and Myofascial Pain Syndrome Diagnosis plus alot of other evil sidekick diagnosis to go with...my question is what happened to make it flip? Is that normal...did Hashimotos cause it? My doctor is on vacation for week so...sitting limbo. Thanks for any insight!