A 30-year-old woman complaining of tiredness was seen by her physician. A serum sample was collected at 2 pm. The following results were obtained (reference ranges are given in brackets):
TSH 1.3 mU/L (0.5–5)
Free T4 15 pmol/L (9–22)
Cortisol 220 nmol/L (>550 at 9 am)
The physician has asked for advice regarding the interpretation of the results and any further investigations you would recommend.
What advice would you give to the physician?