Name of the Test:
Melatonin, Urine Test
N-acetyl-5-methoxy-tryptamine; sleep hormone
The pineal gland has been called a neuroendocrine transducer because of its importance in photoperiodism. The major hormone of the pineal gland is Melatonin(N-acetyl-5-methoxy-tryptamine). It is the major indole compound synthesized by the pineal gland. It is converted from Serotonin by Hydroxy Indole-O-Methyl Transferase. It is excreted into the urine as 6-Sulfatoxymelatonin, N-Acetyl Serotonin, other glucuronide and sulfate forms, and also a small amount as unconjugated “free” Melatonin. Melatonin has potent melanocyte contracting properties. Melatonin is primarily secreted during the dark (night) cycle. Levels drop dramatically after exposure to bright light. Melatonin binds to various proteins including Albumin. Patients with cancer frequently have decreased levels of Melatonin as do patients with impaired central nervous system function. Elevated levels can be found in sympathetic orthostatic hypotension. Melatonin has a stimulatory and suppressive feedback on Gonadotropin release depending on Melatonin levels. Altered levels of Melatonin have been reported with sleep disorders, jet lag, depression, stress, schizophrenia, hypothalamic amenorrhea, pregnancy, anorexia nervosa, immunological disorders, as well as sexual maturation during puberty.
Urine samples are extracted and dried under nitrogen prior to the immunoassay. Melatonin is measured by a competitive enzyme immunoassay (EIA) using anti-melatonin and biotinylated melatonin.
Specimen requirements: 20 ml aliquot of 24 hr urine (2 ml minimum). Total volume per 24 hour collection (in ml) is required for reporting. Urine samples should be refrigerated during collection process.
Shipping requirements: Ship the samples frozen or in ice packs. Shipping samples at room temperature is not recommended.
Turnaround time: Once per week (set up every Friday and reported the following day).
Reference Range: 50 – 150 ng per 24 hrs (collection of urine)
1. Terzieva DD, Mateva ND, Vladimirova-Kitova LG (2009) Melatonin reference limits at 3:00 AM and 8:00 AM in healthy adults. Clin Lab 55: 359 -361.
2. Waldhauser F, Weiszenbacher G, Tatzer E et al (1998) Alterations in nocturnal serum melatonin levels in humans with growth and gaining. Clin Endocrinol Metab 66: 648 -652.
3. Tsolaki M, Karamouzis M, Fountoulakis KN et al (2000) Are serum Melatonin levels a marker for the differential diagnosis of Dementia? German J Psychiatry 3: 1 -11.