This document summarizes melatonin, including its definition, biosynthesis, metabolism, secretion levels, physiological roles, and adverse effects. Melatonin is a hormone produced by the pineal gland that regulates sleep cycles and helps protect against oxidative stress and cancer growth. It is generated from the amino acid tryptophan and serotonin. Peak levels occur between 11PM and 3AM and help induce sleep. While it has various beneficial roles, excess melatonin can cause side effects like daytime sleepiness and hormonal issues.

1. M. Sc. Razhan S. Othman
HOD medical lab
technique

2.  Define of melatonin.
 Biosynthesis and metabolism of melatonin.
 melatonin secretion and it levels and how it
work?
 Physiological role of melatonin .
 Adverse effect .

3. What is melatonin?
 Hormone that is naturally produced by the
pineal gland.
 Arone lerner in 1958 was discovered this
hormone.
 Pinal gland ,in humans resembling the shape
of a pine cone ,its location is either central in
the brain .
 The pineal weight in humans brain is 100-
150mg ,whereas in rat 1-1.5mg.

4. Biosynthesis:
 Generated from amino acid tryptophan and
serotonin
 Is made predominantly at night in the pineal
gland.
 Tryptophan hydroxylase activity where
presence in the mitochondrial
increase during darkness
about 2 fold.
melatonin

6. Metabolism :
 There are several metabolic pathways:
1-brain :one is the formation of N-acetyle-
5methoxykynurenamin after dioxygenase of melatonin
compound cleavage pyrol cycle.
2- liver : by dimethylation to N-acetyl serotonin.
**Metabolism pathway of exogenously administrated
melatonin in humans are reported half-lives 3 and 45
minute.

7. Melatonin secretion
 Melatonin secretion starts at 3-4 months of age
when nighttime sleeping consolidates.
 Peak levels at 1-3 years of age.
 Slightly lower levels through early adulthood.
 Marked decline in levels afterwards.
 Peak levels for 70 year olds is ¼ of levels for
young adults.

8. How melatonin works??
 Melatonin levels cycle
 Low levels during daylight, rise during
nighttime
 Peak levels between 11PM and 3AM
 Levels continue to cycle in constant darkness
 Can slowly adjust to environmental changes

10. Physiological role of melatonin
1-Radical scavenger
2-Sleep
3-Cancer
4-Immune system
5-Other

11. Radical scavenger
 Free radical =bearing one unpaired electron.
 Hydroxyl free radical (OH.), Is one of dangerous and reactive
radical.
 5% of all O2 taken in will be converted to superoxide anion O2.-
 Oxidative stress: continuous forming radical .e
 Oxidative stress can be increase by toxin,
excessive exercise, radiation, infection,
ischemia etc.
 Vitamin C and E also can act as radical
scavenger.

15. Sleep
 Melatonin is “opening the sleep gate “
 Suprachiasmatic Nucleus (SCN) is the site of
internal biological clock.
 Elevated melatonin level occur at night
coincident with sleep humans.
 Melatonin is not to be a direct soporific.

16. Cancer
 Melatonin is inhibitory action of tumor growth.
 The apparent melatonin induced suppression of
prolactin , when prolactin is a hormone that can
promote mammary cancer.
 Several studies reported that ,during the initial
state of tumor development ,melatonin is
increased an early stage of cancer with malignant
cells that do not growth.
 The relationship between pineal gland and cancer
is a dynamic.
 Doses of 10-20mg of melatonin to advanced
cancer patients in the afternoon.

17. Immune system
 Melatonin hormone directly effect of the
immune system when suppression of melatonin
production by propranolol or the inhibitor of
serotonin biosynthesis Para-
chlorophenylalanin resulted in reduced
immune responses toward T-dependent
antigens.

18. OTHER FUNCTION
 Melatonin can act as an antioxidant .
 Exogenous melatonin decrease leptin production .
 Reported that melatonin intake reduced blood
pressure during sleep ,without effect of the heart
rate.
 An important property of melatonin is its ability
to influence circadian rythmicity .
 One of the claimed action of melatonin that anti-
aging effect.
 Melatonin supplements by humans with jet lag,
delay sleep phase(alzheimers disease), epilepsy.

19. Adverse effects
 Excess melatonin can lead to daytime
sleepiness, impaired mental and physical
performance, hypothermia, and high levels of
prolactin
 Menstrual irregularities, impotence decreased
libido.