Endocrine System
The endocrine system is one of the body’s main systems
for communicating, controlling and
coordinating the body’s work
Endocrine System
• Control system that works along with the nervous system to
regulate body functions and maintain homeostasis.
Endocrine System
Nervous System
• slower response (minutes to hrs.)
• potentially long duration of
effects (hours to days)
• works via chemical signals
(“hormones”) which are released
through interstitial fluid into
blood capillaries
• affects multiple cells throughout
the body that have specific
hormone receptors (“target
cells”) resulting in change of
metabolic activities of cells (ex.
affects protein synthesis)
• quick response (milliseconds)
• relatively short duration of effect
• works via electrical impulses
(action potentials) and direct
release of chemicals
(neurotransmitters) across
interstitial fluid to adjacent cells
• affects specific sets of cells
(neuron, muscle, gland) resulting
in specific responses (ex. muscle
contraction or glandular
secretion)
Endocrine System Vocabulary
• Endocrinology – Science that deals with a group of ductless
glands and the action of their secretions which are
transported via the blood stream
• Hormones - chemical messengers carried by the blood from
endocrine glands to the cell upon which they act. (target cells)
• The word “hormone” is derived from a Greek term that
means to arouse to activity.
• Endocrine glands vs. Exocrine glands
• Exocrine glands secrete their products through ducts that
lead to an open space
• Salivary glands, Sweat glands, Gastric glands, Sebaceous
gland glands
• Endocrine glands secrete hormones directly into the
bloodstream , no ducts involved
• Thyroid gland, Pituitary, Parathyroid, Pancreas,
Adrenals…
Endocrine gland
Overview of Endocrine System
• Endocrine system includes all endocrine cells,
tissues, and endocrine glands (organs) of the body
• System of ductless glands that secrete hormones–
chemical messengers/molecules
• Circulate in blood
• Act on target cells
• Target cells respond to the hormones for which
they have receptors
• Effects are dependent on the programmed
response of the target cells
• Hormones are just molecular triggers
Overview of Endocrine System
• Some organs are primarily endocrine organs/glands
(pituitary, thyroid, parathyroid, adrenal, pineal)
• Many different organs have some endocrine
cells/tissues within their structure, but the organ’s
primary function is not endocrine (ie: heart, kidney,
digestive organs, pancreas, hypothalamus, gonads,
thymus)
Classification of Hormones
• Hormones classified based on their chemical structure
Steroid Based
Non-Steroid Based
Steroids, lipid-like
compounds derived
from cholesterol
• Lipid-soluble can
pass through cell
membrane
• requires
intracellular
receptors (bind to
receptors within
the cell) and can
directly affect the
structure or
function of the cell,
via affect on
protein synthesis
&/or energy
production
Amino Acid Derivatives
•
•
•
Peptide hormones
Water soluble and do not enter the cell
requires membrane receptors –(bind to
receptors on cell membrane) triggering a
cascade of biological activity
enzymes catalyzes a reaction that produced a
second messenger molecule that oversees
additional intracellular changes that
promotes a response of the target cell
Other: Prostaglandins
• Local, or tissue,
hormones
• Derived from lipid
molecules
• Do not travel in the
bloodstream
• Target tissues are
located close by
• Produced by organs
such as
Kidneys
Heart
Stomach
Uterus
Brain
Secretion, Distribution &
Effect of Hormones
 Hormones are released on demand – only when needed
 Hormone release is primarily regulated by negative feedback
mechanisms

changes in ECF (ISF/plasma) concentration/composition

changes in circulating levels of hormone itself or regulating
hormones

neural stimuli
 Hormones secreted by endocrine cells into interstitial fluid, and
distributed through bloodstream
 Only cells that posses receptors for that particular hormone can be
affected -“target cell/target organ”
 Effect of hormones is on the metabolic activity of cells, via
activation/inactivation of specific genes, or affecting protein
synthesis
Secretion, Distribution &
Effect of Hormones
Mechanisms of hormone release
•
Humoral: substances other than hormones control the secretion of
endocrine glands ( nutrient, ion level)
•
•
Neural: nervous system stimulates the endocrine gland to release
hormone
Hormonal: hormones from one gland stimulate the release of hormones
from another gland
Hypothalamus & Pituitary Gland
The pituitary gland, or hypophysis:
• is an endocrine gland about the
size of a pea and weighing 0.5 g
(0.02 oz.)
• It is a protrusion off the bottom of
the hypothalamus at the base of
the brain
• rests in a small, bony cavity (sella
turcica) of the spheniod bone at
the base of the brain
• is connected to the hypothalamus
small tube called the infundibular
stem (Pituitary stalk).
• has two functional lobes : the
anterior and posterior pituitary
• secretes hormones that regulate
homeostasis.
Hormones released from the
Pituitary Gland
Pituitary Gland – Posterior lobe
Hormones: released
hormones made by the
hypothalamus
• Oxytocin
• Contractions uterus
• “let down” reflex – milk
ejection
• Antidiuretic Hormone
• Retention of water
• Vasopressin effect ,
increase BP by constricting
arterioles
Pituitary Gland – Anterior lobe
Growth Hormone
• Stimulates cells to grow &
divide
• Fat broken down to use as
energy
• Maintain blood sugar
homeostasis
Insulin-Like Growth Factor - 1
• Bone growth
• Protein synthesis
Liver and other
tissues
Pituitary Gland – Anterior lobe
Prolactin (PRL)
• Stimulates/maintains
milk production
• Unknown function in
males
Pituitary Gland – Anterior lobe
Gonadotropic Hormones:
Follicle-Stimulating Hormone (FSH) &
Luteinizing Hormone (LH) also known as
Interstitial Cell Stimulating Hormone (ICSH)
• Regulate hormonal activities of
gonads
Ovaries:
Estrogen
• Uterine lining growth
• Develop/maintain secondary sex
characteristics
Progesterone
• Uterine lining growth
Testes:
Androgens (Testosterone)
• Supports sperm and secondary sex
characteristics
Ovary
Testicle
Pituitary Gland – Anterior lobe
Thyrotrophic hormone or
Thyroid Stimulating Hormone
(TSH)
• Influences growth & activity of
thyroid
Thyroxine (T4)
• Stimulates metabolism
Triiodothyronine (T3)
• Stimulates metabolism
Calcitonin
• Decrease calcium levels
Pituitary Gland – Anterior lobe
Adrenocorticotropic hormone (ACTH)
• Regulates activity of adrenal
cortex
Androgens
Glucocorticoids
•
•
•
•
•
Cortisone & cortisol
Increase blood glucose
Control inflammation
Decrease edema
Reduce pain
Adrenal medulla
Epinephrine & Norepinephrine
•
Mineralocorticoids/Aldosterone •
• Regulate water and electrolyte
•
balance
•
Long-term Stress Response
Increase heart rate
Increase blood glucose
Increase BP
Increase metabolic rate
Short-term Stress Response
Hormones released from the
Pituitary Gland
Pineal Gland/Pineal Body
Also known as the “third eye”
Found in roof of the third
ventricle of the brain
Melatonin
• Involved in rhythmic activities
(day/night and seasonal)
Parathyroid gland
Tiny masses of glandular tissue
found on posterior surfaces of
thyroid gland
Parathyroid hormone (PTH) or
Parathormone
• Increases blood calcium
levels
• Stimulates osteoclasts to
break down bone matrix to
release calcium into the
blood
Parathyroid gland
Thyroid gland
Thymus Gland
Posterior to sternum, superior to
the heart
Large in infants and children,
decreases in size throughout
adulthood
Thymosin
• Programs “T” cells (Lymphocytes
– a type of white blood cell)
• Plays role in immunity
Pancreas Islets
(Islets of Langerhans)
• Formerly known as Islets of
Langerhans or islands of
Langerhans, irregularly shaped
patches of endocrine tissue
located within the pancreas
Insulin (released from beta cells)
• Reduces blood glucose level
• Increases ability of cells to transport
glucose across cell membrane
Glucagon (released from alpha cells)
• Raises blood glucose level
Other Hormone Producing
Tissue and Organs
Placenta
Temporary organ
Human Chorionic
Gonadotropin
• Stimulates production of
estrogen and progesterone
for maintenance of uterine
lining
Other Hormone Producing
Tissue and Organs
Stomach
Gastrin
• Stimulates glands to release
hydrochloric acid (HCl)
Duodenum
Intestinal Gastrin
• Inhibits HCl secretion
Secretin
• Aids in functions related to
digestion effecting pancreas, liver
and stomach
Cholecystokinin (CCK)
• Aids in functions related to
digestion effecting pancreas, gall
bladder and duodenum
Other Hormone Producing
Tissue and Organs
Kidneys
Erythroprotein
• Effects bone marrow
stimulates red blood cell
production
Vitamin D3 (Calcitriol)
• Aids in the active transport of
dietary calcium across
intestinal cell membrane
Other Hormone Producing
Tissue and Organs
Heart
Atrial Natriuretic Peptide (ANP)
• Affects kidney by decreasing
sodium reabsorption and
releasing renin (enzyme that
aid in increasing BP)
• Affects adrenal cortex
decreasing secretion of
aldosterone
Endocrine gland & Hormone review
A.
• Name the gland.
• Identify the
hormone(s)
released from
gland.
• Mechanism of
stimulus/Regulated
by?
Endocrine gland & Hormone review
B.
• Name the gland.
• Identify the hormone(s) released form
gland.
• Mechanism of stimulus/Regulated by?
Endocrine gland & Hormone review
C.
• Name the gland.
• Identify the hormone(s) released form
gland.
• Mechanism of stimulus/Regulated by?
Endocrine gland & Hormone review
D.
• Name the gland.
• Identify the hormone(s) released form
gland.
• Mechanism of stimulus/Regulated by?
Endocrine gland & Hormone review
E.
• Name the gland.
• Identify the hormone(s) released from
gland.
• Mechanism of stimulus/Regulated by?
Endocrine gland & Hormone review
F.
• Name the gland.
• Identify the
hormone(s)
released form
gland.
• Mechanism of
stimulus/Regulated
by?
Endocrine gland & Hormone review
G.
• Name the gland.
• Identify the hormone(s)
released form gland.
• Mechanism of stimulus?
Endocrine gland & Hormone review
H.
• Name the gland.
• Identify the hormone(s) released from
gland.
• Mechanism of stimulus/Regulated by?
Endocrine Review
Matching I
1. _____ Stimulate development
of the follicle in the ovaries
2. _____ Stimulates the kidney
to reabsorb water from urine
3. _____ Stimulates the thyroid
gland
4. _____ Stimulates the adrenal
cortex
5. _____ Promotes protein
synthesis necessary for growth
A. FSH
B. GH
C. ACTH
D. TSH
E. ADH
Endocrine Review
Matching II
1. _____ Increases blood glucose
levels
2. _____ Decreases blood
calcium levels
3. _____Regulates body
metabolism
4. _____ Increases blood calcium
levels
5. _____Regulate electrolyte
balance
A. Aldosterone
B. Glucagon
C. Thyroxine
D. Calcitonin
E. Parathyroid
hormone
Endocrine Review
• Review chart in text pp. 270-271 to review major
glands, hormone(s) released, hormone(s) chemical
class, their actions and means of regulation.
Continue on to learn about Factors that Affect
Endocrine Function
Factors that Affect Endocrine Function
Everyone's body undergoes changes, some natural
and some not, that can affect the way the endocrine
system works. Some of the factors that affect
endocrine organs include:
• aging
• illness
• stress
• the environment
• and genetics.
Aging
Despite age-related changes, the endocrine system functions well in
most older people. However, some changes do occur because of
normal damage to cells during the aging process and genetically
programmed cellular changes. These changes may alter the following:
• hormone production and secretion
• hormone metabolism (how quickly excess hormones are broken
down and leave the body, for example, through urination)
• hormone levels circulating in blood
• biological activities
• target cell or target tissue response to hormones
• rhythms in the body, such as the menstrual cycle
Aging
• For example, increasing age is thought to be related to the
development of Type II diabetes. With aging, the target cell response
time becomes slower, especially in people who might be at risk for
this disorder.
• The signs and symptoms of endocrine system diseases affect many
body systems. In elderly persons, they are frequently subtle and may
be harder to detect than in younger persons. At times, these signs are
incorrectly linked with other causes, such as the changes of normal
aging, other medical disorders or conditions, or drug therapy.
• The aging process affects nearly every gland. For example, the
hypothalamus is responsible for releasing hormones that stimulate
the pituitary gland. During aging, there is either impaired secretion of
some hypothalamic hormones or impaired pituitary response. These
changes appear to influence the endocrine system's ability to respond
to the body's internal environment. As a result, the body cannot
respond as well either to internal or external stresses
Aging
• With increasing age, the pituitary gland can become smaller
and more fibrous and may not work as well. For example,
production of growth hormone may decrease. This may lead
to a hormone imbalance that causes problems such as
decreased lean muscle, decreased heart function, and
osteoporosis.
• Aging can affect a woman's ovaries. These organs eventually
exhibit the most common endocrine change related to aging:
menopause. In menopause, the ovaries stop responding to
follicle-stimulating hormone and luteinizing hormone from the
anterior pituitary. Ovarian hormone production of estrogen
and progesterone slows down and then stops. Eventually a
woman stops having her periods altogether
Illness
Illness may affect endocrine system function in several ways.
Acute or chronic conditions may change endocrine functions.
Chronic/Acute Conditions
• Hormones are cleared from blood during their circulation to
the target tissues. The liver and kidneys are primarily
responsible for clearing hormones. Several clearance
processes become altered or slowed in individuals who have
chronic heart, liver, or kidney disorders.
• Acute physical or mental stressors can trigger a
preprogrammed stress response. The stress response is
complex and can influence heart, kidney, liver, and endocrine
system function.
Endocrine Pathologies
Endocrine pathologies can result from the following:
• congenital (birth) or genetic defects
• surgery
• traumatic injuries
• cancerous and non-cancerous tumors
• infection
• autoimmune destruction (the immune system turns against the
body's own organs and causes damage)
• In general, endocrine pathologies create a hormone imbalance
typified by either hyposecretion (underproduction) or
hypersecretion (overproduction) of hormones. The underlying
problem may be the endocrine gland itself or a source outside the
gland.
Stress
Many factors can start the stress response, but physical stressors are most
important. In order for the body to respond to, and cope with, physical
stress, the adrenal glands make more cortisol. If the adrenal glands do not
respond, this can be a life-threatening problem. Some medically important
factors causing a stress response are as follows:
• trauma (severe injury) of any type
• severe illness or infection
• intense heat or cold
• surgical procedures
• serious diseases
• allergic reactions
• Other types of stress include emotional, social, or economic, but these
do not require the body to produce high levels of cortisol in order to
survive the stress.
External Factors
• An environmental endocrine disruptor (EED) is a substance
outside of the body that may cause adverse effects to normal
function of the endocrine system. Some EEDs mimic natural
hormone binding at the target cell receptor. These substances
start the same processes between body cells that the natural
hormone would start. EEDs of this type are referred to as
hormone agonists.
• Other EEDs block cellular events associated with hormone
binding. These EEDs are called hormone antagonists. Still
other EEDs can directly interfere with the production, storage,
release, transport, clearance, binding, or elimination of
endogenous hormones in the body. This can greatly affect the
function of certain body systems.
External Factors
There are currently over 84,000 commercial synthetic chemical substances
in use around the world. At least 30,000 have been introduced into the
U.S. environment since 1979. We do not know the extent to which they
can interfere with the endocrine system and cause endocrine system
diseases. Based on our knowledge of the effects of certain synthetic
chemicals, such as DDT, diethylstilbestrol and PCBs, and the increasing
evidence that reproductive function in wildlife and humans is changing,
scientists are now examining a broad range of chemical effects.
EEDs can affect people and animals in many ways:
• disrupted sexual development
• decreased fertility
• birth defects
• decreased hatching in animals
• reduced immune response
• neurological and behavioral changes, including reduced stress tolerance
Genetics
• Portions of your endocrine system can be affected by genes. Genes
are units of hereditary information passed from parent to child.
Genes contain the instructions for the production of proteins, which
are some of the essential components of the body. Genes are
contained in chromosomes. The normal number of chromosomes is
46 (23 pairs).
• Sometimes extra, missing, altered, or damaged chromosomes can
result in diseases or conditions that affect hormone production or
function. The 23rd pair, for example, is the sex chromosome pair.
The mother and father each contribute a sex chromosome to the
child. Girls have two X chromosomes (one from the mother and one
from the father), while boys have one X (from mother) and one Y
(from father) chromosome. Sometimes, however, a chromosome or
piece of a chromosome may be missing. In Turner syndrome, only
one normal X chromosome is present and this can cause poor
growth. In another example, a child with Prader-Willi syndrome
(PWS) may be missing all or part of chromosome 15, which also
affects growth, metabolism, and puberty.
Genetics
• Your genes also may place you at increased risk for certain
diseases, such as breast cancer. Taking estrogen can cause
breast tissue to grow faster. Cancer usually appears in fastgrowing tissue. This is one of the ways that scientists believe
that taking estrogen for symptoms of menopause may be
related to developing breast cancer. Another idea is that
breast tissue breaks down estrogen into chemicals that can
bind to DNA (genetic material) and damage it. Damage to DNA
is a common cause of cancer. At this time, it is not known
exactly why estrogen might cause breast cancer or what role it
does play in breast cancer growth.
Cycles of Hormone Release
Time appears to affect the release of certain types of hormones. Some
hormones have a typical cycling pattern of release. This pattern often
fits with daily body rhythms or the sleep-wake cycle.
• Cortisol builds up early in the day, decreases toward evening, rises
again toward the end of sleep, and peaks during the morning hours.
• Thyroid-stimulating hormone (TSH) peaks during sleep and reaches
its low point three hours after an individual awakens.
• Levels of growth hormone (GH) are high 90 minutes after sleep
begins. GH typically increases during the first 2 hours of deep sleep.
It also increases if a person is hypoglycemic (low blood sugar),
starving, exercising, excited or is a victim of severe injury.
• There is a very definite rise-and-fall pattern to both estrogen and
progesterone activity during a woman's menstrual cycle, which lasts
an average of 28 days.
Endocrine disorders: Classification of
endocrine system disorders
The broad classification of endocrine system diseases
is based on the hormonal secretions.
• Hypersecretion by endocrine glands (Excessive
secretion of hormones)
• Hyposecretion by endocrine glands (Insufficient
secretion of hormones)
• Cancer or tumors in the endocrine gland
In summary
• The endocrine system includes all of the
glands of the body and the hormones
produced by those glands. The glands are
controlled directly by stimulation from the
nervous system as well as by chemical
receptors in the blood and hormones
produced by other glands. By regulating
the functions of organs in the body, these
glands help to maintain the body’s
homeostasis.