Dried Urine LCMS Neurotransmitters

Dopamine is a catecholamine neurotransmitter synthesised from tyrosine via DOPA in dopaminergic neurones of the substantia nigra and ventral tegmental area. It governs motor control, reward processing, motivation, and executive function. Peripherally dopamine is produced in the adrenal medulla and sympathetic ganglia, and urinary excretion reflects whole-body turnover rather than synaptic concentrations in the central nervous system.

Urinary dopamine provides a peripheral window on catecholamine metabolism, used to assess patterns in mood disorders, attention-deficit/hyperactivity presentations, and Parkinson disease. Interpretation is exploratory — low patterns may correlate with reduced motivation or focus, high patterns with agitation or mania, but causality is not established.

Norepinephrine is synthesised from dopamine by dopamine beta-hydroxylase in noradrenergic neurones of the locus coeruleus and in the adrenal medulla. It mediates arousal, vigilance, and the sympathetic stress response. Urinary norepinephrine reflects peripheral sympathetic activity and adrenal secretion rather than brain synaptic levels.

Urinary norepinephrine patterns are used to explore stress-axis activation, anxiety, and sympathetic tone. Elevated levels may accompany chronic stress or phaeochromocytoma (the latter requires plasma or 24-hour urine metanephrines for diagnosis); low levels can suggest adrenal insufficiency or blunted stress response, though dried-urine results are not interchangeable with plasma or 24-hour standards.

Epinephrine is synthesised from norepinephrine by phenylethanolamine N-methyltransferase, an enzyme largely confined to the adrenal medulla. It is the principal hormone of the acute stress 'fight-or-flight' response, raising heart rate, blood pressure, and glucose mobilisation. Urine concentrations reflect adrenal output.

Urinary epinephrine is interpreted alongside norepinephrine to assess adrenal and sympathetic function. Extreme elevations warrant investigation for catecholamine-secreting tumours via plasma or 24-hour urine metanephrines. In the functional-medicine setting, patterns are used to infer stress resilience and sympathoadrenal balance, recognising the exploratory nature of single dried-urine samples.

Serotonin is an indoleamine synthesised from tryptophan, predominantly in enterochromaffin cells of the gastrointestinal tract (>90 per cent of body stores) and in serotonergic neurones of the raphe nuclei. It modulates mood, sleep, appetite, and gastrointestinal motility. Urinary serotonin reflects peripheral turnover and does not cross the blood–brain barrier.

Urinary serotonin offers an indirect, exploratory measure of tryptophan–serotonin metabolism. Low patterns are sometimes linked to depressive symptoms, insomnia, or impulsive behaviour, though peripheral levels do not predict central serotonin availability. Very high urinary serotonin raises suspicion of carcinoid tumour and should prompt measurement of 5-hydroxyindoleacetic acid (5-HIAA) and plasma chromogranin A.

Glutamate is the principal excitatory neurotransmitter in the central nervous system, synthesised from glutamine by mitochondrial glutaminase. It plays central roles in learning, memory, and synaptic plasticity. Urinary glutamate arises from dietary absorption, gut metabolism, and renal handling rather than from brain release.

Dried-urine glutamate is an exploratory marker with uncertain correlation to central glutamate activity. Elevated peripheral patterns may reflect high dietary intake or gut dysbiosis; proposed links to anxiety, excitotoxicity, or neurodegenerative risk are speculative. Results should not be used to diagnose or exclude neurological disease.

GABA is the principal inhibitory neurotransmitter, synthesised from glutamate by glutamic acid decarboxylase in GABAergic neurones. It regulates neuronal excitability, anxiety, and sleep. GABA does not cross the blood–brain barrier, so urinary levels reflect peripheral production — including gastrointestinal microbial synthesis — rather than brain GABAergic tone.

Urinary GABA is an exploratory, non-validated marker. Low patterns are sometimes associated with anxiety, insomnia, or seizure disorders in functional practice, but peripheral GABA does not reliably predict central nervous system concentrations. Results are not diagnostic and should be interpreted with caution.

Glycine is the simplest amino acid and serves dual roles as an inhibitory neurotransmitter in the spinal cord and brainstem and as a co-agonist at NMDA receptors. It is synthesised from serine and is involved in collagen synthesis, one-carbon metabolism, and detoxification pathways. Urinary glycine reflects whole-body turnover.

Urinary glycine patterns are used in functional assessments of methylation, detoxification capacity, and neuroprotection. Elevated glycine may be seen in rare inborn errors of metabolism (non-ketotic hyperglycinaemia), while low levels are proposed to correlate with sleep disturbance or impaired NMDA receptor modulation, though evidence is limited.