Can you explain the relationship between catecholamines and metanephrines?

Phenol vs ether: The chemical structure of epinephrine, the natural hormone generated in excess by a pheochromocytoma tumor, has an aromatic carbon ring with two adjacent -oh (phenol) groups and a side-chain amino group. Compounds with this structure are called catecholamines. Metanephrine is a metabolite of this hormone, with one phenol converted to an ether (-och3). If elevated, it implies the tumor.

Metabolites.: Catecholamines include Epinephrine (adrenaline), norepinephrine, & dopamine. Epinephrine is metabolized (broken down) to metanephrine, and norepinephrine to normetanephrine. Catecholamine levels can change quickly - just the act of drawing blood can raise them) while metanephrine levels are more consistent.