The endocrinology clinic can be quite challenging at times, but you've had a quiet day so far. The door opens once more, and your next patient comes in: 32-year-old Antonio, who has been referred by his primary care physician. You introduce yourself, shake hands, and ask him to take a seat.

You peruse the referral letter. This states that Antonio's blood pressure was found to be 140/90 mmHg at a routine health checkup. His blood pressure on the following day was 160/95 mmHg. Antonio was asymptomatic, with unremarkable medical and family histories. He was not on any medications and denied using recreational drugs. The examination was unremarkable.

A full blood count, serum sodium, potassium, and calcium levels, fasting plasma glucose, renal profile, liver profile, ECG and chest x-ray were normal. A thyroid profile, serum parathyroid hormone levels and an ultrasound scan of the neck were also normal.

However, abdominal ultrasound revealed a 3.5 × 5 cm mass above the right kidney. The primary care physician suspected this might be a pheochromocytoma, and referred Antonio to your clinic for further management.