The Melatonin Sulfate test specifically targets 6-hydroxymelatonin sulfate (6-OHMS), the primary urinary metabolite of melatonin. Melatonin is a neurohormone secreted primarily by the pineal gland in response to circadian signals. This test measures overnight urinary excretion of 6-OHMS, an indirect marker of endogenous melatonin synthesis and secretion. As melatonin itself has a short half-life and is secreted in a circadian rhythm, direct plasma levels can be highly variable. In contrast, 6-OHMS, which results from the hepatic hydroxylation of melatonin and its subsequent sulfation, is more stable and reliably correlates with overall nocturnal melatonin production.
6-OHMS is typically measured in first-morning urine samples, but the test can also be performed on 24-hour urine samples, if required. This non-invasive biomarker is increasingly utilized in both clinical and research settings to assess circadian phase, pineal gland function, and sleep-related pathologies.
This assay serves as a cornerstone in chronobiological diagnostics and functional medicine protocols and is a component of broader neuroendocrine evaluation panels. The relevance of this biomarker spans multiple disciplines, including sleep medicine, psychiatry, oncology, and endocrinology.
Pathophysiological Insight
The urinary excretion of 6-hydroxymelatonin sulfate (6-OHMS) is a key indicator of pineal gland melatonin production and provides insight into circadian rhythm integrity and sleep-wake regulation. Melatonin is synthesized in the pineal gland from tryptophan via a multi-step enzymatic cascade that involves serotonin as an intermediate. The rate-limiting enzyme in this process is arylalkylamine N-acetyltransferase (AANAT), whose activity is tightly regulated by environmental light cues. Melatonin secretion begins in the evening, peaks during the night (2-4 a.m.), and is suppressed by morning light exposure.
Once secreted, melatonin undergoes hepatic metabolism via cytochrome P450 enzymes (especially CYP1A2) into 6-hydroxymelatonin, which is subsequently conjugated with sulfate in the liver to form 6-OHMS. This metabolite is then excreted in the urine. As more than 70% of melatonin is metabolized through this pathway, 6-OHMS excretion strongly correlates with endogenous nocturnal melatonin production.
Altered urinary 6-OHMS levels reflect various physiological and pathological conditions. Reduced 6-OHMS can suggest pineal gland dysfunction, nocturnal light exposure, neurodegenerative disorders, autism spectrum disorder, or shift work disorder, all of which may be associated with circadian misalignment. Elevated 6-OHMS is less commonly seen but can occur with exogenous melatonin supplementation, enhanced pineal sensitivity, or during acute inflammation and sepsis, where melatonin may be upregulated as an antioxidant and immunomodulator.
Because melatonin influences diverse physiological systems, including immune function, glucose metabolism, and oncogenesis, changes in its production (and by extension, 6-OHMS levels) are increasingly recognized as biomarkers of neuroendocrine, inflammatory, metabolic, and neoplastic pathophysiology.
Clinical Relevance
The urinary measurement of 6-hydroxymelatonin sulfate (6-OHMS) is gaining growing clinical interest across multiple fields of medicine, particularly in settings involving circadian rhythm disruption. The test is relevant in disorders of sleep, neurodevelopment, mood regulation, endocrine balance, oncologic risk, and immune-inflammatory control. Its applications span specialties such as sleep medicine, psychiatry, neurology, pediatrics, functional medicine, and oncology. Clinicians may consider the test in cases of insomnia, autism spectrum disorder (ASD), depression, Alzheimer’s disease, hormone-sensitive cancers, sepsis, burnout, chronic stress, jet lag, and shift work-related circadian misalignment. Although not disease-specific, 6-OHMS offers biologically meaningful insight into pineal gland function and melatonin signaling, making it a valuable supportive tool in the personalized evaluation of circadian dysregulation.
Diagnostic Value
The urinary Melatonin Sulfate Test offers a valuable, non-invasive diagnostic approach for evaluating pineal gland function, melatonin production, and circadian rhythm status. It is particularly relevant in clinical settings where sleep, endocrine, or neurobehavioral regulation is disturbed.
Diagnostic Applications and Target Populations
- Patients with Sleep Disorders: Individuals with insomnia, circadian rhythm sleep-wake disorders, and shift work disorder benefit from this test, as it enables objective confirmation of melatonin deficiency and differentiation between primary insomnia and circadian phase delay. It also helps assess treatment response to melatonin or light therapy.
- Neurodevelopmental Conditions: In children with autism spectrum disorder (ASD) or ADHD, who frequently exhibit reduced melatonin secretion, 6-OHMS levels support the diagnosis of sleep-related comorbidities and help tailor melatonin supplementation strategies.
- Oncologic Screening and Prognosis: Emerging studies link lower urinary melatonin sulfate levels to increased risk of hormone-sensitive cancers, such as prostate and breast cancer. When combined with cortisol (M/C ratio), this test may help stratify cancer risk and progression, though it is considered an adjunctive biomarker rather than a standalone diagnostic tool.
- Critical Care and Sepsis Monitoring: In pediatric and adult sepsis, abnormal melatonin metabolite levels may provide early prognostic information on the inflammatory response or oxidative stress, aiding risk stratification.
- Neurologic and Psychiatric Evaluation: The test supports the evaluation of Alzheimer’s disease, major depressive disorder, and bipolar disorder, in which circadian misalignment is often involved. Measuring 6-OHMS can help direct chronotherapeutic interventions.
Therapeutic Approaches
Therapeutic strategies targeting abnormal 6-hydroxymelatonin sulfate (6-OHMS) levels aim to restore circadian rhythm integrity, ameliorate sleep-related disturbances, and modulate melatonin-mediated physiological pathways, including oxidative stress, immune function, and hormonal balance. Given its ability to quantify endogenous melatonin production, the test serves as a guide for customized interventions, particularly in functional and personalized medicine.
Last update: 27/11/2025
