American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What is the primary effect of metyrosine on the body?

1. Enhances catecholamine synthesis

2. Inhibits catecholamine synthesis

3. Increases blood pressure

4. Stimulates adrenal gland activity

The correct answer is: Inhibits catecholamine synthesis

Metyrosine primarily inhibits catecholamine synthesis by blocking the enzyme tyrosine hydroxylase, which is the rate-limiting step in the production of catecholamines, including dopamine, norepinephrine, and epinephrine. By reducing the levels of these neurotransmitters, metyrosine decreases the physiological effects associated with increased catecholamine levels, such as elevated heart rate and blood pressure. This mechanism is particularly useful in managing conditions associated with excessive catecholamine production, such as pheochromocytoma or other adrenal tumors, where controlling the overproduction of these hormones is crucial for patient management. The therapeutic use of metyrosine underscores its role in reducing the excessive sympathoadrenal activity by effectively limiting the availability of catecholamines for release into the bloodstream.