THE ENDOCRINE SYSTEM

In order to understand how the Endocine System effects hair growth, an
account of what makes up the endocrine system and how this system
functions is necessary.
The endocrine system is a group of ductless glands that regulate bodily
processes by their secretion of chemical substances called hormones.
These hormones act as messangers as they are carried to specific target
organs and tissues, via the blood stream. Some hormones may show their
effects immediately , (ie: adrenalin) while others may take several
years to produce any effects (ie: growth).

The Endocrine System is comprised of the following glands:

THE PITUITARY GLAND
* Also known as the master gland, as it has influence over several other glands.

THE PINEAL GLAND
* Either inhibits or regulates the processes of the pituitary gland and the sex glands (referred to as gonads) until puberty. This gland also coordinates circandian rhythms.

THE PARATHYROID GLAND - (There are four).
* Secretes the hormone known as parathormone. This gland controls and raises the bodies calcium levels.

THE THYROID GLAND
* Effects growth and metabolism, ie: growth of nerve fibres. Reduces levels of calcium in the blood.

THE ADRENAL GLANDS - (There are two).
* Responsible for adrenaline seretion. This hormone (adrenaline) stimulates heart rate and blood pressure.

THE ISLETS OF LANGBRHANS IN THE PANCREAS
* There are three cell types found throughout the pancreas:

Alpha Cells - Secretes the hormone glucagon (converts glycogen to glucose).

Beta Cells - Secretes the hormone insulin (converts glucose to glycogen, reducing glucose levels in the blood).

Delta Cells - Secrete the hormone somatostatin (inhibits the secretion of other hormones, ie: growth).

THE SEX GLANDS - (two ovaries , two testes)
* These glands will be discussed in detail as the hormones secreted
from these glands play a major role in excessive hair growth.

THE OVARIES
The female reproductive glands produce two female hormones, oestrogen
and progesterone, which are responsible in the development of the
reproductive organs and controlling the menstrual cycle. The ovaries
also produce a minimal amount of one particular male hormone known as
androgen. An excess of androgens can cause superfluous hair growth.

The male hormones which cause hair growth in female come from:
- the adrenal glands
- the ovaries
- fat which converts other hormones to male hormones

The adrenal glands secrete androgens when the baby is in the womb but
production ceases shortly after birth and lays dormant until the onset
of puberty. On commencement of puberty, the adrenal glands wake up
and begin producing male hormones once more. Hair follicles (the end
organs) are stimulated therefore resulting in hair growth ie: pubic
hair and hair under the armpits. Excessive amounts of androgens or
sensitive end organs results in superfluous hair growth.

THE TESTES
The male reproductive glands produce hormones collectively known as
androgens. The testicles produce several other steriod hormones
(hormones made up of lipid compounds) which may, in some cases, behave
like mild oestrogens. Testosterone is the chief male hormone which is
responsible for male sexual characteristics.
Although females produce dominating amounts of
determine female characteristics) and males produce
of androgens (which determine male charcteristics)
oestrogens (which dominating amounts both sexes produce
male and female hormanes to some degree.

RESPONSES OF THE END ORGANS
The internal secretions which occur within the endocrine system effect
end organs ie: hair follicles and oil glands.
The End organ, in this case the hair follicle, responds to the most
minute alterations which may occur within the endocrine system.
Hormonal messangers are carried through the blood stream and effects
take place if the end organ responds.
The hair follicle has a receptor site which responds to the hormones
which are responsible for hair growth. These hormones can cause hair
to grow weaker or stronger, alter hair texture and colour, or grow in
lesser or excessive amounts.
However, not all receptor sites will respond to the hormones.
Excessive hair growth is only present if the end organ is sensitive to
a particular hormone. Each individuals varies greatly both internally
and externally. For example, a female of Oriental origin may be prone
to irregular perions due to high levels of androgens. Although levels
of androgens are high, the woman may not develop facial hair. This is
due to the fact that her hair follicles do not actively respond to male
hormones.
However, a Mediterranean woman may develop facial hair as her hair
follicles are more sensitive to androgens. Some women s hair follicles
are so sensitive that excessive hair growth may occur even with a
normal amount of androgens.