Normetanephrine is a metabolite of norepinephrine, which is a blood-regulating hormone (called a catecholamine) released during times of physical or emotional stress, and when found in excess (for long periods) a marker for catecholamine-secreting tumors and also tested during treatments of confirmed tumors and to monitor any recurrence.
Specifically, this test helps determine rare pheochromocytomas and extra-adrenal paragangliomas tumor types, which approx. 25% are related to hereditary alterations in specific genes. Examples include MEN-1 and MEN-2 (Multiple Endocrine Neoplasia, types 1 and 2) syndromes.