Endocrine

Question 1

What is the best SCREENING test for suspected pheochromocytoma? What is the specificity?

Answer 1

PLASMA free metanephrines

Specificity: 85%
False-positives are a problem!

Used to EXCLUDE pheochromocytoma when test results are negative

Question 2

What is MOST reliable test for pheochromocytoma?

What are some confounding factors?

Answer 2

24-hour urine metanephrines

(Used if plasma free metanephrines are positive)

Confounding factors:

Question 3

What are some things that can cause false-positive results in a 24-hour urine catecholamine test for pheochromocytoma?

Answer 3

• sympathomimetics (cold remedies)
• phenoxybenzamine
• acetaminophen
• tricyclic antidepressants

Question 4

What is the role of a clonidine suppression test for pheochromocytoma?

Answer 4

Administration of PO 0.3mg clonidine and measurement of plasma free metanephrine levels is done a in equivocal cases for pheochromocytoma

Question 5

PTH levels: Parathyroid adenoma vs. parathyroid carcinoma

Answer 5

Parathyroid adenoma = rarely above 2x baseline

Parathyroid adenocarcinoma: 3-10x baseline

Question 6

During parathyroid adenoma excision for hyperparathyroidism, you remove suspected adenoma and PTH drops 20%. What is your next step?

Answer 6

bilateral neck exploration to find if there is another parathyroid adenoma