3-Methoxytyramine (3-MT) is a human trace amine that occurs as a metabolite of the neurotransmitter dopamine. It has been shown to act as an agonist of human TAAR1, and an inhibitor of mitochondrial respiration. 3-MT has garnered research interest for its potential links and implications to Parkinson's disease and other Neurological disorders.

Metanephrine (metadrenaline) is a metabolite of epinephrine (adrenaline) created by the action of catechol-O-methyl transferase on epinephrine. It is a commonly occurring, pharmacologically and physiologically inactive metabolite of epinephrine. The measurement of plasma free metanephrines is considered to be the best tool in the diagnosis of pheochromocytoma, a rare kind of adrenal medullary neoplasm. In adrenal chromaffin cells, leakage of norepinephrine and epinephrine from storage granules leads to the substantial intracellular production of the O-methylated metabolite metanephrine. In fact, the adrenals constitute the single largest source out of any organ system including the liver for circulating metanephrine. In humans, about 93 percent of circulating metanephrine is derived from catecholamines metabolized within adrenal chromaffin cells.

S-Adenosyl-L-homocysteine (SAH), a potent methyltransferase inhibitor and a substrate of the s-adenosylhomocysteine hydrolase, is an amino acid derivative and an intermediator or modulator of several metabolic pathways, including the activated methyl cycle and cysteine biosynthesis. It was shown, that the plasma SAH might be a novel biomarker for the early clinical identification of cardiovascular disease. In addition, the elevated SAH in Alzheimer's brain was related to markers of disease progression and cognitive impairment.

1,25-dihydroxycalciferol (1,25-dihydroxyvitamin D2 or ercalcitriol) is a metabolite of vitamin D. It exerts antirachitic activity in animals. 1,25-dihydroxycalciferol and its analogs have antineoplastic actions in vitro.