A 54-year-old patient has presented to her GP with symptoms…

A 54-year-old patient has presented to her GP with symptoms of thyroid disease. Her GP has ordered some thyroid function tests, the results of which are shown below: TSH           8 mu/L         (0.5-5 mu/L) T4             54 mmol/L   (70-140 mmol/L) Which of the following is the most appropriate diagnosis?