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The Endocrine Glands
Their hormones, their target
organs and major functions
The Endocrine system I
Hormones are generally secreted into
the blood and then circulate trough the
body to exert an effect only on their
target cells. They act by binding in a
lock-and-key manner with specific
receptores found only in the target
tissues.
The Endocrine system II
Hormones can be classified as either
steroid or non-steroid.
Steroid hormones are lipid soluble, and
most are formed from cholesterol.
 Non-steroid hormones are formed from
proteins, peptides or aminoacids
The Endocrine system III
Steroid hormones pass trough cell
membranes and bind to receptors inside the
cell. They use a mechanism called direct
gene activation to cause protein synthesis.
Nonsteroid hormones cannot enter the cells
easily, so they bind to receptors on the cell
membrane. This activates a second
messenger within the cell, which in turn can
trigger numerous cellular processes.
Endocrine System:
Steroid Hormone Action
The Endocrine system III
Steroid hormones pass trough cell membranes and
bind to receptors inside the cell. They use a
mechanism called direct gene activation to cause
protein synthesis.
Non-steroid hormones cannot enter the cells easily,
so they bind to receptors on the cell membrane.
This activates a second messenger within the cell,
which in turn can trigger numerous cellular
processes.
Endocrine System:
Non Steroid Hormone Action
The Endocrine system IV
A negative feed-back system regulates
secretion of most hormones.
The number of receptors for a specific
hormone can be altered to meet the body’s
demands. Up-regulation refers to an increase
in receptors and down-regulation in a
decrease. These two processes change cell
sensivity to hormones.
The negative feedback system
A negative feedback system regulates secretion of
most hormones. The major exemples are give by the
hormones which secretion is controlled by pituitary
tropins such as TSH, LH, FSH and ACTH.
The pituitary tropin
secretion is inibited
by raising blood
concentration of
the hormone released
by the tropin target
gland
Pituitary Gland
 tropin
Target gland
Circulating
Hormone
NEGATIVE
FEEDBACK
The negative feedback system
Pituitary Gland
+ tropin
Target gland
Circulating
Hormone
NEGATIVE
FEEDBACK
The Pituitary gland I
Anterior lobe
GH
Growth hormone
Prolactin
ACTH
Adrenocorticotropin
TSH
Thyroid-stimulating hormone
FSH
Follicle-stimulating hormone
LH
Luteinizing hormone
The Pituitary gland II
POSTERIOR
LOBE (from
Hypotahalamus)
ADH Antidiuretic hormone
or Vasopressin
Oxytocin
The Pituitary gland III Anterior lobe
Growth hormone (GH)
TARGET ORGAN
All cells in the body
MAJOR FUNCTIONS
Promotes developement and
enlargement of all body tissues up
through maturation; increases
rate of protein syntesis; increases
mobilization of fats and use of fat
as an energy source; decreases
rate of carbohydrate use
Secrezione e meccanismo di azione del GH
Secrezione di
GHRH e SS
Inibisce GHRH
Stimola SS
Feedback
Ipofisi
Inibisce sintesi
e rilascio di GH
Fegato
GH
IGF-1
Cappa 1999
Bersaglio Cellulare
Secrezione e meccanismo di azione del GH
Secrezione di
GHRH e SS
Inibisce GHRH
Stimola SS
Feedback
Inibisce sintesi
e rilascio di GH
Ipofisi
GH
Fegato ed
altri organi
Azione
diretta
Azione indiretta
Somatomedine
Tessuto Adiposo
Azioni scheletriche
Azioni non scheletriche
Formazione collagene
Aumento sintesi proteica
e crescita cellulare
Induce crescita scheletrica
Rilascio
Trigliceridi
Riduce l’assorbimento
di Glucosio
McArdle 1996
Regolazione della secrezione del GH da parte dei nutrienti
e dei substrati metabolici
Glucosio
FFA
Glucosio
IPOTALAMO
SS
GHRH
Aminoacidi
Intestino
FFA
IPOFISI
GH
Muscolo
Fegato
I GF-1
Gliconeogenesi
TessutoAdiposo
Lipolisi
Sintesi
Proteica
Utilizzazione
del Glucosio
Cappa.M: Endocrin.Eser.Fis. Utet 1999
The Pituitary gland IV
Anterior lobe
HORMONE
TARGET
ORGAN
MAJOR
FUNCTIONS
Thyroid gland
Controls the amount of T3 and
T4 produced and released by
the thyroid gland
ACTH
Adrenal cortex
Controls the secretion of
hormones from the adrenal
cortex
PROLACTIN
Breasts
TSH
Stimulates breasts
developement and milk
secretion
The Pituitary gland V
Anterior lobe
HORMONE TARGET
ORGAN
FSH
LH
Ovaries, Testes
Ovaries, Testes
MAJOR
FUNCTIONS
Initiates growth of follicles inthe
ovaries and promotes secretion of
estrogen from the ovaries.
Promotes developement of sperm
in testes.
Promotes secretion of estrogen
and progesterone and causes the
follicle to rupture, releasing the
ovum. Causes testes to secrete
testosterone
The Pituitary gland VI Anterior lobe
Hypothalamic Controlling Factors
The anterior pituitary gland, also called adenohypophysis,
secretes six hormones in response to releasing and
inibiting factors (peptides) secreted by hypothalamus.
ACTH : stimulated by CRH (corticotropic-realising
hormone)
GH : stimulated by GHRH (growth hormone realising
hormone)
Inibited by SOMATOSTATIN
TSH : stimulated by TRH (thyrotropin-realising hormone)
The Pituitary gland VI Anterior lobe
Hypothalamic Controlling Factors
FSH : stimulated by GnRH (gonadotropin-realising
hormone)
LH : stimulated by GnRH
PROLACTIN : stimulated by PRH (prolactin-realising
hormone)
Inibited by PIH (prolactin-inibiting hormone)
The Pituitary gland VI
Posterior lobe
HORMONE TARGET
ORGAN
ADH
Kidneys
Uterus,
OXYTOCIN Breasts
MAJOR
FUNCTIONS
Assist in controlling water
excretion by the kidneys. Elevates
blood pressure by constricting
blood vessels
Stimulates contraction of uterine
muscles ; milk secretion
The Thyroid gland
HORMONES TARGET
ORGAN
T3 , T4
All cells in
Calcitonin
MAJOR
FUNCTIONS
the body
Increases the rate of cellular
metabolism, increases rate
and contractility of the heart
Bones
Controls calcium-ion
concentraction in the blood
The Parathyroid glands
HORMONE
TARGET
ORGAN
Bones
PTH
(parathormone) Intestines
Kidneys
MAJOR
FUNCTIONS
Controls calcium-ion
concentraction in
extracellular fluid trough
its influence on bones,
intestines and kidneys
The Adrenal gland Medulla
HORMONE
TARGET
ORGAN
Epinephrine
Most cells
in the body
Norepinephrine
MAJOR
FUNCTIONS
Mobilizes glycogen; increases
skeletal muscle blood flow;
increases heart rate and
contractility; oxygen consumption
Constricts arterioles and venules,
thereby elevating blood pressure
The Adrenal gland Cortex
HORMONE
TARGET
ORGAN
Mineralcorticoids
(Aldosterone)
Kidneys
Glucocorticoids
(Cortisol)
Androgens
Most cells
in the body
Ovaries, Testes
MAJOR
FUNCTIONS
Increases sodium retention and
potassium axcretion trough the
kidneys
Controls metabolism of
carbohydrates, fats and proteins;
anti-infiammatory action
Assist in the developement of
female and male sex
characteristics
The Endocrine Pancreas
HORMONE
TARGET
ORGAN
MAJOR
FUNCTIONS
INSULIN
Most cells in the
body
Controls blood glucose levels by
lowering glucose levels
GLUCAGON
Most cells in the
body
Increases blood glucose;
stimulates the breakdown
of protein and fat
Islets of Langherans
SOMATOSTATIN
and gastroDepresses the secretion of both
intestinal tract
insulin and glucagon
GONADS I Testes
HORMONE
TESTOSTERONE
TARGET
ORGAN
Sex organs
MAJOR
FUNCTIONS
Promotes developement of
male sex characteristics
including growth of testes,
Skeletal muscle scrotum and penis, facial hair
and change in voice;
promotes muscle growth
GONADS II
Ovaries
HORMONE
TARGET
ORGAN
Sex organs
ESTROGENS
Adipose
tissue
Bones
MAJOR
FUNCTIONS
Promotes developement of
female sex organs and
characteristics; provides
increased storage of fat;
assist in regulating the
mestrual cycle. Promotes
turn-over of bone tissue
stimulating osteoblastyc
activity
Kidney’s endocrin activity
HORMONE
ERYTROPOIETIN
(EPO)
TARGET
ORGAN
Bone marrow
MAJOR
FUNCTIONS
Stimulates erytrocyte
production and realisig
Hormonal effects on metabolism
and energy I
  Plasma glucose is increased by the combined
actions of glucagon, epinephrine and cortisol.
These hormones promote glycogenolysis and
gluconeogenesis, thus increasing the amount of
glucose available for use as a fuel source.
  Insulin helps the released glucose enter the cells,
where it can be used for energy production.But
insulin levels decline during prolonged exercise,
indicating that exercise facilitates the action of
insulin so that less hormone is required during
exercise than at rest.
Hormonal effects on metabolism
and energy II
  When carbohydrate reserves are low, the body
turns more to fat oxidation for energy, and this
process is facilitated by cortisol, epinephrine and
GH
  Cortsol accelerates lipolisys, realising free fatty
acid into the blood so they can be taken up by the
cells and used for energy production. But cortisol
levels peak and then return to near normal levels
during prolonged exercise. When this happens, the
cathecholamines and GH take over cortisol’s role
Hormonal effects on metabolism
and energy III. ( Fluid balance )
  The two primary hormones involved in the regulation of
fluid balance are Aldosterone and ADH (antidiureti hormone)
  When plasma volume or blood pressure decrease,
kidneys form and release in the blood a proteolitic enzyme
called Renin that converts Angiotensinogen (a liver
producted protein) in Angiotensin I (AT I) , a ten aminoacid
peptide with no byological effects. AT I is then converted in
AT II by the Angiotensin Converting Enzyme (ACE), in all
vascular sides. AT II increases peripheral arterial resistence,
raising blood pressure.
Hormonal effects on metabolism
and energy III. ( Fluid balance )
  AT II also triggers the release of Aldosterone from the
adrenal cortex. Aldosterone promotes sodium reabsorption
in the kidneys, which in turn causes water retention, thus
increasing the plasma volume.
 ADH is released in response to increased plasma
osmolarity. When hypothalamic osmoreceptores sense this
increase, induce the ADH release from the posterior
hypophysis.

 ADH acts on the kidneys promoting water conservation.
Trough this mechanism plasma volume is increased and
blood osmolarity is decreased by dilution of plasma solutes.
The endocrine response to exercise I
HORMONE
EXERCISE
RESPONSE
Catecholamines 
GH


ACTH-Cortisol
TSH-thyroxine
SPECIAL
RELATIONSHIPS
PROBABLE
SIGNIFICANCE
Greater increase with
Intense exercise, NOR >
EP, increase less after
Training
Increased blood glucose
Increases more in unfit person
Declines faster in fit person
Greater increase with intense
Exercise; increase less after
Training with submaximal exercise

Increased thyroxine turnover with
Training but no toxic effects evident
?
Increased gluconeo
genesis in liver
?
The endocrine response to exercise II
HORMONE
LH
Testosterone
EXERCISE
RESPONSE
No change

EstradiolProgesterone

Insulin

Glucagon

SPECIAL
RELATIONSHIPS
None
None
PROBABLE
SIGNIFICANCE
None
?
Increases durig luteal phase
of cycle
?
Decreases less after training
Decreased stimulus
To use blood glucose
Increases less after training
Increased blood glucose
via glycogenolysis and
gluconeogenesis
The endocrine response to exercise III
EXERCISE
RESPONSE
HORMONE
RAS (reninAngiotensin
system)
ADH

Expected 
PTH-Calcitonin
EPO
?
?
SPECIAL
RELATIONSHIPS
Some increase after traning
in rats
None
None
None
PROBABLE
SIGNIFICANCE
Sodium retention to
maintain plasma volume
Water retention to
maintain plasma volume
Needed to estabilish
Proper bone development
Would be important to
increase red blood cell
production
Study Questions I
  What is an endocrine gland and what are the functions of
hormones?
  Explain the difference between steroid and nonsteroid
hormones
  How can hormones have very specific functions when they
reach nearly all parts of the body trough the blood?
  How are plasma levels of specific hormones controlled?
  Explain the relationship between the hypothalamus and the
pituitary gland
  Briefly outline the major endocrine glands, their
hormones and the specific action of these
Study Questions II
  Which of the hormones outlined in previous question are of
major significance during exercise?
  What is hemoconcentration and how does the endocrine
system relate to it?
  Describe the hormonal regulation of metabolism during
exercise. What hormones are involved and how do they
influence the avaliabilty of carbohydrates and fats for energy
during exercise lasting for several hours?
  Describe the hormonal regulation of fluid balance during
exercise
  Whath is hemodiluitio and how does the endocrine system
relate to?