Yes, it's very possible, I began to develop a nervous condition, after TT. Never had panic attacks, but my body always feel as I'm on edge, or drank 25 cups of coffee, cycling from minimal to intense. Also, you may be reacting to Synthroid. My endo shared that patients can have anxiety/panic attacks hypo or hyper. Disuss with physician. Wish you well.
So it just a coincidence that 3 months after your hemithyroidectomy and are on thyroid med you have panic attacks? Not likely. What is your daily synthroid dose? Do you have any other symptoms that you have noticed? Please post your latest thyroid related test results and reference ranges shown on the lab report.