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We and Our HormonesMelanocyte-stimulating hormone

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

pigmentation and control of appetite.

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

amphibians, the hormone is often called

What is melanocyte-stimulating hormone?

Melanocyte-stimulating hormone is a collective name for a group of peptide hormones produced by the skin, pituitary gland and hypothalamus in response to ultraviolet (UV) radiation.

It plays a key role in producing coloured pigmentation found in the skin, hair and eyes.

It does this by inducing specialised skin cells called melanocytes to produce a pigment called melanin; melanin protects cells from DNA damage which can lead to skin cancer (melanoma).

How is melanocyte-stimulating hormone 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.

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

reduce skin inflammation by stimulating the release