Name of the Test: Melatonin, serum/Plasma
Alias Names : 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 hydrolyzed and then extracted / purified prior to the immunoassay .Melatonin is measured by competitive enzyme immunoassay (EIA) using anti-melatonin and biotinylated melatonin.
Specimen requirements: 3 ml of plasma or serum (1 ml minimum).
Patient Preparation: Fasting samples are preferred. Melatonin concentration varies with light and dark cycle. The concentration is lower during the day and high at night. Patients treated with pituitary or steroid hormones influence the concentration. Hence, it should be discontinued for 2 days prior to the collection of samples.
Shipping requirements: Ship the samples frozen in Dry ice.
Turnaround time: 1 week (set up every Tuesday and reported the following day).Repeats are assayed the same week .
Melatonin concentration varies with light and dark cycle. The concentration lower in the day and high during night .Patients treated with steroids and pituitary hormones influence the concentration. Hence, it should be discontinued for 48 hrs prior to collection of samples.
Day time : 2.0 – 80 pg/ml
Night Time : 18.5 – 180 pg/ml
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.