A 46 year-old woman with a history of fibromyalgia presents to the clinic with a complaint of anxiety, frequent diarrhea and occasional palpitations. She also noticed an unexplained loss of weight and irregular menstrual periods over the last 3 months.
What is the most likely laboratory investigation that could lead to a diagnosis in this case?
A-CT scan of the head
B-MRI of the brain
D-Cosyntropin stimulation test
E-Serum Thyroid Stimulation Hormone (TSH) level