msh, melanoma, tans

1. +
We and Our Hormones
Melanocyte-stimulating hormone

2. Melanocyte-stimulating
hormone
Melanocyte-stimulating hormone
describes a group of hormones
produced by the pituitary gland,
hypothalamus and skin cells. It is
important for protecting the skin from
UV rays, development of

3. MSH in Amphibians
 In some animals such as the claw-toed
frog Xenopus laevis production of MSH is
increased when the animal is in a dark
location. This causes pigment to be
dispersed in pigment cells in the toad's
skin, making it become darker, and harder
for predators to spot. The pigment cells are
called melanophores and therefore, in

5. Whatis melanocyte-stimulating hormone?
 Melanocyte-stimulatinghormoneisacollectivenameforagroupofpeptide
hormonesproducedbytheskin,pituitaryglandandhypothalamusin
responsetoultraviolet(UV)radiation.
 Itplaysakeyroleinproducingcolouredpigmentationfoundintheskin,hair
andeyes.
 Itdoesthisbyinducingspecialisedskincellscalledmelanocytestoproducea
pigmentcalledmelanin;melaninprotectscellsfromDNAdamagewhichcan
leadtoskincancer(melanoma).

7. How ismelanocyte-stimulatinghormone
controlled?
Melanocyte-stimulating hormone production is
increased by exposure to UV light.
Due to the many other functions of melanocyte-
stimulating hormone besides melanin production, there
are likely to be a number of other factors that regulate
its production.
This means that, unlike most hormones, melanocyte-
stimulating hormone release is not thought to be
controlled by a direct feedback mechanism.

8. Tanning
α-MSH is responsible for tanning in humans.
When ultraviolet light strikes skin cells
(keratinocytes), it activates the transcription
factor p53.
p53 turns on transcription of the gene encoding
POMC.
Cleavage of the POMC protein produces
α-MSH:- This is secreted from the cells and
stimulates nearby melanocytes
to synthesize melanin in packets called
melanosomes. The melanosomes are transferred to
the skin cells where they form a protective cap over
the nucleus. This cap helps protect the DNA within
the nucleus from the damaging effects of UV
radiation.
ACTH:-This is secreted into the blood and may help