Melatonin (N-acetyl-5-methoxytryptamine) is a hormone synthesized in the pineal (pineal) gland in the brain from tryptophan via the intermediate serotonin. Melatonin controls the day-night rhythm. It is only synthesized at night. The maximum production is between two and four o’clock. Daylight inhibits production, so it is released in a pulsatile manner. Melatonin is metabolized in the liver and excreted in the urine. The metabolite 6-hydroxymelatonin sulfate is measured in urine and correlates closely with serum melatonin levels.
Melatonin-induced deep sleep is a stimulant for the release of the growth hormone somatotropic hormone (STH) (synonyms: somatotropin, Human Growth Hormone (hGH)).
The concentration of melatonin changes with age. Young infants have low levels and continuous release, toddlers have high normal levels. Thereafter, secretion progressively decreases.
The process
Material needed
- Nocturnal collection urine with morning urine
Preparation of the patient
- Not known
Disruptive factors
- Not known
Standard values
| Age | Normal values |
| Infants | 1,400 pmol/l |
| Adult | 260 pmol/l |
Indications
- Suspected disturbances of the sleep-wake rhythm.
Interpretation
Interpretation of increased values
- Liver cirrhosis – connective tissue remodeling of the liver with functional impairment.
- Drug therapy with antidepressants (MAO inhibitors and tricyclic antidepressants).
- Pinealoma – tumor originating from the pineal gland.
Interpretation of decreased values
- Alcohol dependence
- Depression
- Jet lag
- Drug therapy with beta-blockers (antihypertensives – high blood pressure drugs).
- Mammary carcinoma (breast cancer)
- Paraplegic syndrome
- Shift work
- Schizophrenia
- Sleep disorders
- Winter depression
Other hints
- Decreased nocturnal melatonin synthesis, determined as the ratio of 6-hydroxymelatonin sulfate to creatinine in first morning urine, may be an indicator of impending myocardial infarction (heart attack), especially in obese women.
- Melatonin is also used therapeutically in studies, for example, jet lag.
