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LEVEL 3 DIPLOMA IN AROMATHERAPY
MODULE 13
KNOWLEDGE OF ANATOMY, PHYSIOLOGY & PATHOLOGY FOR
COMPLEMENTARY THERAPIES
THE ENDOCRNE SYSTEM
MODULE 6
COURSE MANUAL
CHRISTINA LYNE
[email protected]
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Aromalyne Training
Level 3 Diploma in Aromatherapy (ABC)
THE ENDOCRINE SYSTEM
The endocrine system has many functions: it works closely with the nervous system
and plays an important part in homeostasis, coordinates growth and development
and affects reproduction and metabolism. The endocrine system is composed of
ductless glands which produce hormones, the body’s chemical messengers. Each
gland produces specific hormones.
WHAT IS A HORMONE?
A hormone is a chemical messenger, made of protein, which is secreted directly into
the bloodstream by a particular gland. They are produced in the gland and are then
transported to the area / organ they control or affect. Hormones evoke a response
in other cells or tissues of the body that are located far away. Some hormones have
a slow action over a period of years, while others produce a quick response. They
are produced a little at a time when they are needed and are not secreted
continuously.
STRUCTURE OF ENDOCRINE GLANDS
An endocrine gland is a ductless gland which produces hormones. Ductless means
that there is no separate canal or tube to transport the hormones to the blood. They
are not physically connected to each other and may be widely separated from each
other. Endocrine glands are groups of secretory cells surrounded by an extensive
network of capillaries that allow the hormones to diffuse from the secretory cells into
the bloodstream.
The main endocrine glands are as follows:
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1 pituitary gland
1 hypothalamus
1 pineal gland
1 thyroid gland
4 parathyroid glands
2 adrenal glands
the islets of Langerhans (in the pancreas)
1 thymus gland
2 ovaries (female)
2 testes (male)
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Level 3 Diploma in Aromatherapy (ABC)
WHAT DO HORMONES AND THE ENDOCRINE SYSTEM DO?
Hormones and the Endocrine System affect the behaviour and function of different
areas of the body and of the body overall. For example, hormones are responsible
for correct growth, changes in puberty, the menstrual cycle, pregnancy, the
menopause, responses to stress and danger and the proper functioning of the
kidneys and digestive system.
Below is an overview of the physiology of the Endocrine System:
Hormone Producing Cell
Feedback Signal
(usually negative
feedback)
Disposal of
hormone by
degradation
and/or excretion
Blood
Desired Response
(Target Cell)
The amount of hormone released by the endocrine gland or tissue is determined by
the body’s need for the hormone at any given time. This is the basis to which the
endocrine system operates. Hormone producing cells have available to them
information from sensing and signaling systems that permit them to regulate the
amount and duration of hormone release. Secretion is regulated so that there is no
over/under production of the hormone.
Once the hormone is released it is carried by the blood to target tissues and organs
that contain target cells (cells which respond to the hormone). All cells are target
cells for one or more hormones but not all cells respond to a particular hormone.
Target cells contain receptors that bind the hormone so that it can produce an effect.
Once the target cell responds to the hormone, the response must be recognised by
the secretory cell by a feedback signal.
WHAT HAPPENS TO THE HORMONE ONCE IT HAS DONE ITS WORK?
Once a hormone has done its work, it is rendered inactive by its target cells. It is
carried to the liver. There it is deactivated and broken down. It is then eliminated.
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THE INDIVIDUAL ENDOCRINE GLANDS
THE PITUITARY
This is the master gland. It is a pea-sized mass made up of two parts: a larger
anterior lobe and a smaller posterior lobe. Both lobes rest in a depression in the
sphenoid bone behind the nose and between the eyes. It is attached to the
hypothalamus by a stalk-like structure. It releases at least nine hormones that have
important effects on the body. Some of these control body functions directly; others
trigger different hormones to produce hormones of their own.
THE HYPOTHALAMUS
The hypothalamus is situated at the base of the brain above the pituitary and is
connected to the pituitary by nerve fibres. It secretes hormones (called ‘releasing
factors’) which are transmitted to the pituitary. The pituitary gland then produces
hormones which control other endocrine glands. The hypothalamus and the pituitary
gland work together to co-ordinate and control hormone production.
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The hypothalamus:
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Controls body temperature
Motivates sexual behaviour
Stimulates appetite and thirst
Determines mood and emotions
Regulates sleep
Monitors hormone levels in the blood
THE PINEAL GLAND
This tiny little gland is found in the centre of the brain. Its function isn’t fully
understood, but it is believed to be associated with the inhibition of growth and
development of the reproductive organs before puberty. It responds to sunlight. It
secretes a hormone called melatonin that controls our body rhythms such as
sleeping and waking. It is also believed to affect our appetite, fertility and growth.
THE THYROID GLAND
This gland is made up of two lobes and is located in the front of the neck, just below
the larynx. It is under the control of the pituitary gland. The function of the thyroid is
to take iodine, found primarily in seaweed and sea water fish, and convert it into
thyroid hormone. Thyroid cells are the only cells in the body that can absorb iodine.
Every cell in the body depends upon thyroid hormones for regulation of their
metabolism. Unlike other glands, it can store the hormones it produces. It also
secretes calcitonin.
THE PARATHYROID GLANDS
There are four glands, two either side behind the thyroid. They produce the hormone
parathormone. The sole purpose of these glands is to control calcium levels within
the blood. They also control how much calcium is in the bones, and therefore, how
strong and dense the bones are. As the blood filters through the parathyroid glands,
they detect the amount of calcium present. If too much calcium is present, the
hormone calcitonin is released from the thyroid, preventing the removal of calcium
from the bones. If calcium levels are insufficient, parathormone will trigger calcium
to be released from bones and into the blood. Calcium is also the primary element
which causes muscles to contract and is important in blood clotting.
THE ADRENAL GLANDS
There are two adrenal glands, each one located on the top of each kidney. Each
gland is triangular in shape and is made up of two regions: an inner medulla and an
outer cortex. Each region produces different hormones.
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Adrenal Cortex:
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Mineralcorticoids help to control the correct balance of water, sodium and
potassium in the body. The hormone responsible for most mineral corticoid
activity is aldosterone. It inhibits the amount of sodium excreted in the urine
into the blood. Sodium reabsorption is also accompanied by retention of
water and therefore aldosterone is also involved in the regulation of blood
volume and blood pressure too.
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Sex Corticoids comprise the female sex hormones oestrogen and the male
hormones androgens. They are produced in small amounts and help to
control the changes in males and females in late puberty and early adulthood.
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Glucocorticoids are essential to life, regulating metabolism and responses
to stress.
The main hormone secreted by the adrenal cortex is cortisol. It is stimulated by
ACTH (adrenocorticotrophic hormone) from the anterior pituitary and by stress.
Cortisol has several functions:
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Gluconeogenesis - cortisol causes the breakdown of proteins which are then
released as amino acids into the blood stream. The liver then uses these
amino acids to make glucose. This same process also raises blood sugar
levels (hyperglycaemia) that provides the brain with glucose.
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Lipolysis - causes the breakdown on triglycerides into fatty acids and
glycerol for energy production. It promotes the absorption of sodium and
water from the renal tubes and causes an anti-inflammatory action.
Adrenal Medulla
The medulla is completely surrounded by the cortex. It produces the hormones
adrenaline and noradrenaline. Both these hormones are released into the blood
stream when the sympathetic nervous system is stimulated. They are structurally
very similar and together are responsible for the fight or flight response by:
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Increasing heart rate & blood pressure
Decreasing rate of digestion
Diverting blood to essential organs, including the brain, heart and skeletal
muscles.
Dilating pupils
Adrenaline has a greater effect on the heart whereas noradrenaline has more
influence on blood vessels.
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THE PANCREAS
This gland is located a little below the stomach, between the duodenum and the
spleen. It has two main functions:
1. to produce pancreatic endocrine hormones
2. to produce pancreatic digestive enzymes
The cells which make up the islets of Langerhans are found in clusters scattered
throughout the pancreas. Blood glucose levels are controlled by the opposing
actions of insulin and glucagon:
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Insulin decreases blood glucose levels. If there is too much sugar in the
blood, insulin is released causing the liver and muscles to store glucose (in
the form of glycogen).
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Glucagon increases blood glucose levels. If there is insufficient sugar in the
blood, or the body needs a rush of sugar for energy (an athlete about to run
around the track) glucagon will cause the liver and muscles to release
glucose into the bloodstream to restore levels.
THE THYMUS GLAND
The thymus lies behind the sternum and extends upwards into the root of the neck.
It is made of lymphoid tissue. It produces several hormones, including thymosin,
that are important in early life to assist with growth. It gradually degenerates after
puberty. It plays an important role in immunity and is involved in the development of
T-lymphocytes which help the body to fight viruses and infections.
THE OVARIES
These are the female glands and are found either side of the pelvic cavity. Each is
attached to the upper part of the uterus by a short ligament, is about the size of an
almond and is pinky grey in colour. They produce:
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Oestrogens which are responsible for the secondary sex characteristics in the
female.
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Progesterone which stimulates the lining of the uterus to thicken for possible
implantation of an embryo and to prepare the mammary glands for milk
production.
During pregnancy large amounts of oestrogens and progesterone are produced by
the placenta preventing ovulation and menstruation and maintaining the thick lining
of the uterus.
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THE TESTES
These are the male glands and are found in the groin, in the scrotum. The testes
produce the hormone testosterone responsible for male sexual characteristics and
for the development of secondary sexual characteristics such as the deepening of
the voice and beard growth.
LOCAL HORMONES
A number of body tissues not normally described as endocrine glands secrete
substances that do not travel to remote organs but act in tissues nearby (locally).
They are:
Histamine
This is released as part of the inflammatory response, increasing capillary
permeability and causing vasodilation. It also causes contraction of smooth muscle
of the bronchi and alimentary tract and stimulates the secretion of gastric juice.
Serotonin
This substance is present in platelets - It is a local vasoconstrictor. When platelets
come into contact with a damaged blood vessel, their surface becomes sticky and
they attach themselves to the damaged wall. They then release serotonin which
restricts the blood vessel, thereby reducing blood flow through it.
In the brain - it plays a role in the brain and nerve function. It has an effect on mood.
Serotonin leads to feelings of happiness / relaxation / sleepiness. It is concentrated
in certain areas of the brain - the hypothalamus and mid brain contain large
amounts.
In the intestinal wall - it causes intestinal secretion. The stomach is surrounded by
cells which release serotonin. This causes intestinal peristalsis.
Erythropoietin
This hormone is made in the kidneys and increases the rate of red blood cell
formation (erythropoiesis).
HOMEOSTATIC FEEDBACK MECHANISMS
Many endocrine glands are linked to neural control centers by homeostatic feedback
mechanisms. The two types of feedback mechanisms are negative feedback and
positive feedback. Most endocrine glands are under the control of negative
feedback mechanisms.
Negative feedback mechanisms act like a thermostat in the home. As the
temperature falls, the thermostat detects the change and triggers the central heating
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to turn on and heat the house. Once the temperature reaches its thermostat setting,
the heating turns off.
An example of negative feedback is the regulation of the blood calcium level. The
parathyroid glands secrete parathyroid hormone, which regulates the blood calcium
amount. If calcium decreases, the parathyroid glands sense the decrease and
secrete more parathyroid hormone. The parathyroid hormone stimulates calcium
release from the bones and increases the calcium uptake into the bloodstream from
the collecting tubules in the kidneys. Conversely, if blood calcium increases too
much, the parathyroid glands reduce parathyroid hormone production. Both
responses are examples of negative feedback.
Positive feedback mechanisms have the effect of amplifying the stimulus and
increasing the release of the hormone until a particular process is complete and the
stimulus ceases.
An example of positive feedback can be found in childbirth. The hormone oxytocin
stimulates and enhances labour contractions. As the baby moves towards the birth
canal, pressure on the receptors within the cervix send messages to the brain to
produce oxytocin.
Oxytocin travels to the uterus through the bloodstream,
stimulating the muscles in the uterine wall to contract stronger. The contractions
intensify and increase until the baby is outside the birth canal. When the stimulus to
the pressure receptors ends, oxytocin production stops and labour contractions
cease.
THE INTER-RELATIONSHIP BETWEEN THE ENDOCRINE AND NERVOUS
SYSTEMS
The hypothalamus is the link between the nervous system and the endocrine
system. It produces hormones which regulate hormone secretion by the pituitary
gland. The pituitary gland then produces hormones which control other glands. The
hypothalamus is connected by nerve fibres to many areas of the brain and receives
information from them about the emotions and about conditions in other parts of the
body.
What is the difference between Endocrine and Exocrine Glands?
Exocrine glands are glands that secrete their products through the ducts, and
discharge it into the external environment, to organs or the outside the body.
Exocrine glands differ from endocrine glands, because they have ducts that deliver
the products in the superficial part of the body, such as the skin, or in the inner part
where they are necessary, such as the pancreatic juice that is carried into the
intestine to aid digestion. The glands that are found in the body are mostly exocrine
glands. Examples of exocrine glands are sweat, saliva and mammary glands, as well
as oil and enzymes.
Exocrine glands manufacture and release hormones.
These hormones are
transported to the surrounding area, and to the blood. A specific receptor is then
needed for that hormone to do its specified job.
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Level 3 Diploma in Aromatherapy (ABC)
The Endocrine system is one of the body’s most important systems, especially with
the control of the body’s functions. This is how the body communicates and
coordinates with the nervous system, reproductive system, pancreas, liver, kidneys
and fat to maintain balance, or homeostasis, with reproduction, growth and
development, and energy levels and responses to external stress and injury.
Endocrine glands produce hormones that can be used inside the body. The
endocrine transmits the hormonal messages to cells by secreting them into the
blood and extracellular fluid. A receptor is needed in order to receive the message
transmitted. The target points may be cells, tissues or organs.
Endocrine glands are ductless, therefore the secreted hormones are released into
the interstitial spaces that surround the cells. The hormones are delivered to the
nearest capillaries, and spread throughout the body. The responses are delayed
because hormones must first travel through the blood to reach the target organs.
The duration is longer because the kidneys filter the blood.
THE CHANGES IN OUTPUT OF SPECIFIC HORMONES THAT OCCUR DURING
PUBERTY, THE MENSTRUAL CYCLE, PREGNANCY AND MENOPAUSE
Puberty (male)
This occurs between the ages of 10 - 14 years. LH (luteinising hormone) from the
anterior pituitary gland stimulates the increase in production of testosterone. This
hormone is responsible for the development of the body to sexual maturity.
Puberty (female)
Between the ages of 12 - 14 years, young girls are at the stage where their internal
organs have matured sufficiently and they can bear children. The ovaries are
stimulated by the hormones FSH (follicle stimulating hormone) and LH (luteinising
hormone) secreted by the anterior pituitary. Increased secretion of these hormones
stimulates the ovaries to secrete oestrogens, responsible for the secondary sexual
characteristics. The breasts begin to develop and the uterine tubes, uterus and
vagina grow.
The Menstrual Cycle
This event occurs every 26 - 30 days throughout the childbearing period (approx. 36
years). The hypothalamus secretes LHRH (luteinising hormone releasing hormone)
which stimulates the anterior pituitary to release FSH and LH. Together, these
hormones promote ovulation and stimulate the ovaries to produce oestrogens and
progesterone. Oestrogens and progesterone stimulate and prepare the uterus to
receive, nourish and protect a fertilised ovum (egg). If the ovum is not fertilised a
new cycle begins.
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Pregnancy
For pregnancy to occur, the ovum is fertilised. During the first 3-4 months, the
ovaries continue to secrete high levels of oestrogens and progesterone to thicken
the lining of the uterus and to prepare the breasts for lactation. Progesterone inhibits
uterine contraction. Prolactin levels increase during pregnancy in preparation for
lactation, but high levels of oestrogens and progesterone prevent this from actually
happening. The ovaries and the placenta also secrete inhibin, which prevents the
secretion of follicle stimulating hormone (thus preventing egg production). At the
end of the pregnancy progesterone levels fall so that uterine contractions can
happen. Oxytocin (posterior pituitary gland) is responsible for stimulating uterine
contraction. The ovaries and placenta now secrete relaxin to help the cervix to dilate
and to relax the various joints and ligaments involved in labour. Levels of
oestrogens and progesterone decrease after the birth, allowing lactation to
commence.
Menopause (female)
The menopause usually occurs between the ages 45 - 55 years. And this marks the
end of the childbearing period. The ovaries become less responsive to FSH and LH
and ovulation and the menstrual cycle become irregular and eventually stop
altogether. In some, this can happen suddenly or over a period of years sometimes as long as 10 years! It is caused by a progressive reduction in oestrogen
levels.
Menopause (male)
In males, there is no period comparable to the female menopause. However, at
about the age of 55 years, the production of testosterone declines and with it
reduced muscle strength, fewer viable sperm and decreased sexual desire occurs.
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OTHER BODY TISSUES THAT HAVE AN ENDOCRINE FUNCTION
These include:
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The heart
The kidneys
The skin
The liver
HEART
The heart has an intrinsic system whereby the cardiac muscle is automatically
stimulated to contract without the need for a nerve supply from the brain. However,
the intrinsic system can be stimulated by circulating chemicals such as hormones.
The hormones adrenaline and noradrenaline, secreted by the adrenal medulla, have
the same effect as sympathetic stimulation i.e. they increase the heart rate.
Thyroxine increases heart rate.
KIDNEYS
The formation of new red blood cells is called erythropoiesis. The primary stimulus
to increased erythropoiesis is a condition called hypoxia i.e. deficient oxygen supply
to body cells. Hypoxia increases the formation of red blood cells by stimulating the
hormone erythropoietin, produced mainly by the kidneys.
SKIN
Sex hormones influence sebaceous glands and hair follicles. Androgen hormones
(male hormones) in women and testosterone in men have a direct influence on
sebaceous secretion and the production of acne. When sebaceous gland activity
increases with the production of excess sebum then acne is formed.
In later life, oestrogens (which antagonize the effect of androgens) and male
hormones slow down in production, which in turn influences sebaceous secretions
and creates a drier skin.
LIVER
The liver is an extremely active organ with many functions. Two of these functions
have an endocrine function:
Carbohydrate Metabolism converts glucose to glycogen in the presence of insulin
and then converts glycogen back to glucose in the presence of
glucagon
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The above changes are important in the regulation of the blood glucose level. After
a meal, the blood in the portal vein has a high level of glucose content and insulin
converts some of it to glycogen for storage. Glucagon converts this glycogen back
to glucose as required, to maintain the blood glucose level.
Inactivation of hormones - these include insulin, glucagon, cortisol, aldosterone,
thyroid and sex hormones.
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The Glands
The Hypothalamus gland
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Their Hormones
Their Actions
Corticotrophin releasing
hormone (CRH)
Targets the adrenal
glands and triggers the
adrenals to release ACTH
Thyroid stimulating
hormone releasing
hormone (TRH)
Targets the thyroid where
it functions to synthesize
and release thyroid
hormones T3 and T4
Follicle stimulating
hormone releasing
hormone (FSHRH)
Targets the ovaries and
the testes where it
enables the maturation of
the ovum and of the
spermatozoa
Luteinizing hormone
releasing hormone (LRH)
Targets the ovaries and
testes and its receptors
are in cells which promote
ovulation and increase
progesterone synthesis
and release
Growth hormone
releasing hormone
(GHRH)
Targets the anterior
pituitary to release growth
hormones to most body
tissues, increase protein
synthesis and increase
blood glucose
Prolactin inhibiting
hormone (PIH)
Targets the anterior
pituitary to inhibit milk
production at the
mammary gland
Prolactin releasing
hormone (PRH)
Targets anterior pituitary
to release milk production
at the mammary gland
Melanocyte inhibiting
hormone (MIH)
Targets skin pigment cells
(melanocytes) to regulate
pigmentation
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The Pituitary gland
(Anterior lobe)
(Posterior lobe)
Human growth hormone
(HGH)
Regulates height and
growth
Thyroid Stimulating
Hormone (TSH)
Stimulates normal
development
and secretion of the
thyroid
Adrenocorticotrophin
(ACTH)
Stimulates the adrenal
cortex and releases
corticosteroids
Follicle-stimulating
hormone (FSH)
Stimulates ovaries to
produce oestrogens and
to ovulate
Prolactin (PRL)
Stimulates milk
production
Luteinising hormone (LH)
Stimulates production of
oestrogens, progesterone
and testosterone
Melanocyte-stimulating
hormone (MSH)
Stimulates release of
melanin
Oxytocin (OT)
Stimulates uterine
contraction, triggers milk
production
Vasopressin - anti-diuretic Reduces urine production
(ADH)
and raises blood pressure
The Thyroid gland
The Parathyroid glands
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Thyroxine
Stimulates tissue
metabolism,
growth and development
Calcitonin (CT)
Maintenance of calcium
and
phosphorous balance
Parathormone (PTH)
Stimulates calcium
reabsorption in the
kidneys, activates
Vitamin D
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The Pineal gland
Melatonin
Controls body rhythms
The Adrenal glands
Mineral Corticoids (mainly
Aldosterone)
Regulates
sodium/potassium
balance in the body
Glucocorticoids (mainly
Cortisol)
Regulates metabolism
Plays a role in immunity
and inflammation, helps
to resist long-term stress.
Sex hormones
(Androgens &
Oestrogens)
Stimulates sexual
development & maturity,
ovulation, pubic hair
Adrenaline &
Noradrenaline
Prepares the body for
‘fight or flight’ response.
The Thymus
Thymosin
Helps fight
viruses/infections
The Pancreas
Insulin
Helps glucose enter the
cells, thus reducing the
level of glucose in the
blood.
Glucagon
Raises glucose levels in
the blood by releasing
glucose from the liver
Somatostatin
Inhibits insulin and
glucagon release, slows
absorption of nutrients
from the gastrointestinal
tract
Oestrogens
Responsible for female
characteristics e.g. breast
growth, widening of hips,
pubic hair. Together with
Progesterone, they
regulate the female
reproductive cycle.
Progesterone
Helps maintain
The Ovaries
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pregnancy. Together with
Oestrogen it regulates the
female reproductive
cycle.
The Testes
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Testosterone
Responsible for male
characteristics e.g.
changes at puberty voice breaking, pubic &
facial hair, sperm
production, stimulates sex
drive.