I was diagnosed with hyperthyroidism/Graves disease about 20 years ago. It was diagnosed and treated by an endocrinologist. My Dr. told me that hyperthyroidism can flip to hypothyroidism over time. (My mother experienced this exact situation.) So I would ask for a referral to an endocrinologist. Thyroid issues are one of their specialties. They can order the appropriate tests, recommend treatment and provide ongoing monitoring. My Dr. continues to monitor me for any changes that need to be addressed.