HP Profile — Urine Neurotransmitter Panel (Sanesco)

Serotonin is synthesised from dietary L-tryptophan via 5-hydroxytryptophan (5-HTP) through the sequential actions of tryptophan hydroxylase (TPH) — which requires iron, tetrahydrobiopterin (BH4), and molecular oxygen as cofactors — and aromatic L-amino acid decarboxylase (AAAD), which requires pyridoxal-5-phosphate (vitamin B6). Approximately 90–95% of total body serotonin is produced by enterochromaffin cells of the gastrointestinal tract, making urinary serotonin a predominantly peripheral and enteric biosynthesis marker rather than a reflection of central serotonergic neurotransmission. Serotonin is catabolised by monoamine oxidase A (MAO-A) to 5-hydroxyindoleacetic acid (5-HIAA), the primary urinary metabolite.

Urinary serotonin is assessed in the Sanesco HP Profile as a marker of peripheral serotonin synthesis capacity, informing decisions about L-tryptophan or 5-HTP precursor support and cofactor sufficiency (B6, iron, zinc, magnesium). In Sanesco's clinical framework, reduced urinary serotonin is associated with depressive symptoms, sleep dysregulation, anxiety, and impaired impulse control, and guides targeted amino acid therapy. Practitioners must communicate to patients that urinary serotonin does not directly measure CNS serotonergic activity — the blood-brain barrier prevents peripheral serotonin from entering the CNS and urinary levels do not validate SSRIs, nor can they diagnose depressive disorder. The clinical utility of this marker lies in nutritional and precursor guidance within an integrative framework.

GABA is the principal inhibitory neurotransmitter of the central nervous system, synthesised from glutamate via glutamic acid decarboxylase (GAD) in a reaction requiring pyridoxal-5-phosphate (vitamin B6) as an essential cofactor. Urinary GABA is produced peripherally — from pancreatic beta cells, gastrointestinal enteroendocrine cells, immune cells, and renal tubular cells — and does not cross the blood-brain barrier from the periphery, meaning urinary output reflects peripheral GABA production rather than central inhibitory tone. Magnesium, zinc, and taurine are cofactors and modulators of GABAergic signalling relevant to functional supplementation protocols.

In Sanesco's framework, urinary GABA is interpreted in relation to urinary glutamate as a proxy for the peripheral inhibitory-to-excitatory balance, informing supplementation with GABA precursors, B6, magnesium, L-theanine, and taurine in patients with anxiety, sleep disturbance, muscle tension, and stress reactivity. Low GABA relative to glutamate in functional medicine is associated with a pattern of excitatory dominance. Practitioners should communicate the blood-brain barrier limitation clearly — oral GABA supplementation does not directly enter the CNS under normal physiological conditions, and peripheral urinary GABA does not represent central GABAergic inhibitory function.

Dopamine is synthesised from L-tyrosine via L-DOPA through the sequential actions of tyrosine hydroxylase (TH — requiring tetrahydrobiopterin, iron, and molecular oxygen) and aromatic L-amino acid decarboxylase (AAAD — requiring B6). Urinary dopamine derives from renal tubular synthesis and local renal dopaminergic signalling (which regulates sodium excretion), peripheral sympathetic neurons, adrenal medullary secretion, and intestinal enteroendocrine cells — with central dopaminergic neurons contributing negligibly due to blood-brain barrier exclusion. Dopamine is catabolised to homovanillic acid (HVA) via COMT and MAO-B pathways; copper is a cofactor for dopamine-beta-hydroxylase in the subsequent conversion to norepinephrine.

In Sanesco's clinical framework, urinary dopamine reflects peripheral catecholamine synthesis capacity from tyrosine, guiding precursor supplementation with L-tyrosine or L-phenylalanine. Low dopamine output in functional interpretation is associated with reduced motivation, executive dysfunction, fatigue, and mood dysregulation. Markedly elevated urinary dopamine warrants clinical consideration of catecholamine-secreting tumour (phaeochromocytoma, paraganglioma) before functional attribution — particularly when accompanied by elevated norepinephrine and epinephrine. Urinary dopamine is not a validated surrogate for mesolimbic, nigrostriatal, or mesocortical dopaminergic pathway activity.

Norepinephrine is synthesised from dopamine by dopamine-beta-hydroxylase (DBH) — an enzyme requiring ascorbic acid (vitamin C) and copper as cofactors — within sympathetic nerve terminals and the adrenal medulla. Urinary norepinephrine derives predominantly from peripheral sympathetic nervous system spillover into the circulation, reflecting sympathoadrenal tone at the time of collection. It is catabolised by MAO and COMT to normetanephrine and vanillylmandelic acid (VMA). Urinary norepinephrine is subject to diurnal variation and is significantly elevated by physical activity, psychological stress, and caffeine.

In Sanesco's framework, urinary norepinephrine is assessed alongside epinephrine as a marker of sympathoadrenal output and adrenergic tone, relevant to chronic stress evaluation, autonomic nervous system characterisation, and adrenal-sympathetic depletion patterns. Low norepinephrine alongside low dopamine in the context of fatigue and motivational impairment is interpreted as catecholamine precursor depletion. Elevated norepinephrine — particularly when chronic — is associated with sustained sympathetic activation and is addressed through adrenal support, stress reduction, and precursor balance.

Epinephrine is synthesised exclusively in the adrenal medulla from norepinephrine by phenylethanolamine-N-methyltransferase (PNMT), a reaction that requires high local cortisol concentrations from the adjacent adrenal cortex for PNMT induction — establishing a direct biochemical link between glucocorticoid output and adrenomedullary catecholamine production. Urinary epinephrine therefore specifically reflects adrenomedullary secretory activity, mechanistically distinct from the sympathetic neuronal source of urinary norepinephrine.

In Sanesco's framework, urinary epinephrine provides a specific marker of adrenomedullary output, contextualising the broader catecholamine pattern alongside dopamine and norepinephrine. Suppressed epinephrine alongside low norepinephrine and low cortisol is consistent with adrenomedullary depletion in the context of prolonged HPA and sympathoadrenal activation — a pattern functional medicine practitioners address with adrenal support protocols. Markedly elevated epinephrine warrants formal investigation to exclude phaeochromocytoma before functional interpretation is applied.

Glutamate is the primary excitatory neurotransmitter of the central nervous system and is simultaneously central to peripheral nitrogen metabolism, the urea cycle, and protein catabolism. Urinary glutamate derives largely from renal tubular amino acid metabolism and dietary protein catabolism rather than central glutamatergic synaptic activity. It serves as the direct biosynthetic precursor to GABA via glutamic acid decarboxylase, making its ratio to urinary GABA the key interpretive metric in Sanesco's inhibitory-excitatory balance framework.

In Sanesco's framework, disproportionately elevated urinary glutamate relative to GABA is interpreted as excitatory dominance — associated with anxiety, hyperreactivity, poor stress tolerance, and sleep disturbance — and guides supplementation aimed at enhancing GABAergic conversion: B6 (GAD cofactor), magnesium, L-theanine, and taurine. Pyridoxal-5-phosphate deficiency specifically impairs glutamate-to-GABA conversion, producing elevated glutamate output that Sanesco's interpretive framework identifies as a cofactor insufficiency signal actionable through B6 repletion.

Glycine is the simplest amino acid and serves multiple biological roles — as an inhibitory neurotransmitter acting at strychnine-sensitive glycine receptors in the spinal cord and brainstem, as the most abundant amino acid in collagen (approximately 33% of collagen residues), as a substrate for glutathione synthesis alongside cysteine and glutamate, and as a participant in one-carbon metabolism and bile acid conjugation. Urinary glycine reflects a composite of protein catabolism, hepatic glycine conjugation reactions, and renal tubular handling rather than direct central glycinergic neurotransmission.

In Sanesco's framework, urinary glycine is assessed as a marker of glycine availability for inhibitory neurotransmission, collagen integrity, and glutathione synthesis capacity. Low urinary glycine may guide supplementation with glycine, which has evidence for improving sleep quality — particularly slow-wave sleep — and may have anxiolytic properties. Glycine supplementation is gaining clinical traction in integrative neurology for sleep support and spasticity management.

Histamine is synthesised from L-histidine by histidine decarboxylase in mast cells, basophils, gastric enterochromaffin-like cells, and intestinal bacteria. Urinary histamine reflects peripheral histamine production and catabolism — gut microbiome composition and dietary histamine load are the dominant determinants of urinary output. Central histaminergic neurons (arising from the tuberomammillary nucleus of the posterior hypothalamus and projecting throughout the brain) regulate the sleep-wake cycle, appetite, and cognitive alertness, though they contribute negligibly to urinary histamine output.

Sanesco includes histamine as a neuroactive amine with relevance to neuroinflammation, sleep-wake regulation, and immune activation. In functional interpretation, elevated urinary histamine points to histamine intolerance, mast cell hyperactivation, gut dysbiosis with histamine-producing bacterial overgrowth, or DAO (diamine oxidase) enzyme insufficiency — and guides dietary histamine reduction and DAO enzyme supplementation. Low histamine is interpreted as reduced histaminergic activation. Dietary high-histamine food intake in the 48 hours before collection is the dominant confounding factor.

β-Phenylethylamine is a trace amine synthesised from L-phenylalanine by aromatic L-amino acid decarboxylase (AAAD). It acts as an endogenous neuromodulator and TAAR1 (trace amine-associated receptor 1) agonist, stimulating monoamine release and potentiating dopaminergic and noradrenergic synaptic activity. PEA has an extremely short half-life due to rapid MAO-B catabolism to phenylacetic acid — making urinary PEA a composite reflection of synthesis rate and MAO-B catabolism rather than tissue concentration.

In Sanesco's framework, urinary PEA is assessed as a marker of endogenous trace amine activity, with reduced output associated with mood dysregulation, attention difficulties, and motivational impairment. MAO-B enzyme activity is the primary determinant of PEA catabolism — MAO-B inhibitors (including selegiline and certain flavonoids) raise PEA by reducing its breakdown. In integrative practice, PEA assessment guides phenylalanine and tyrosine precursor support. # REVIEWER FLAG: PEA clinical utility as a urinary marker has limited mainstream evidence base — reviewer to assess whether additional interpretive caveating is required.