A 24-year-old woman presents with symptoms of unquenchable thirst after being prescribed 60mg prednisone for seven days in the treatment of contact dermatitis. Dipstick of her urinalysis reveals a specific gravity of 1.004 that is otherwise normal.

She does not care for the taste of tap water and therefore drinks bottled water, which allows her to confidently say she drinks ten or more liters per day. Uric acid levels are found to be 420 µmol/L. Glycosylated Hemoglobin is 5.4%.

Which of the following are the most appropriate diagnosis and first step?

A. Cushing syndrome – MRI
B. Diabetes insipidus – Consult
C. Diabetes mellitus – Start PO Med
D. Parkinson disease – Consult neurology
E. Psychogenic polydipsia – Consult psych